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Sketch a function from its derivatives

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53501112
A function \(f\) satisfies \(f'(x)=\ln(3)\) for every real \(x\). Which candidate graph could represent \(f\)? Justify your choice.
Figure for problem 535011

Hints

- Determine whether the constant derivative is positive, negative, or zero. - A derivative that never changes value imposes a very specific shape on the original graph. - Use the sign of the derivative to decide which direction the graph must move.

Solution

1. Since \(3>1\), \(\ln(3)>0\). Thus \(f'\) is a positive constant. 2. A constant positive derivative means \(f\) is a line with constant positive slope. 3. Only graph a has that form, so graph a could represent \(f\).

Answer

Graph a
55616412
Instead of a freehand sketch, give an exact **graph blueprint**. A differentiable function satisfies \(f(0)=1\), \(f'(x)<0\) for \(x<0\), \(f'(0)=0\), \(f'(x)>0\) for \(x>0\), and \(f''(x)>0\) for every real \(x\). Describe the graph from left to right. Your blueprint must state the monotonicity and concavity on each side of \(x=0\), and identify the type and coordinates of the point at \(x=0\).

Hints

- The sign of \(f'\) gives the direction of travel. - A negative-to-positive change in \(f'\) gives a local minimum. - The sign of \(f''\) gives concavity. - Use \(f(0)=1\) to place the landmark vertically.

Solution

1. Since \(f'(x)<0\) for \(x<0\), the graph decreases as it approaches \(x=0\) from the left. 2. Since \(f'(x)>0\) for \(x>0\), the graph increases to the right of \(x=0\). Thus \(f'\) changes from negative to positive, so \(x=0\) is a local minimum. 3. The anchor \(f(0)=1\) makes the minimum point \((0,1)\). 4. Because \(f''(x)>0\) everywhere, both the left and right branches are concave up. Blueprint: decreasing and concave up to \((0,1)\), then increasing and concave up.

Answer

Decreasing and concave up for \(x<0\); local minimum at \((0,1)\); increasing and concave up for \(x>0\).
53234912
The graph shows two functions, \(f\) and \(g\). One graph represents a function, and the other represents its derivative. Decide which graph represents the function and which represents the derivative. Justify your answer.
Figure for problem 532349

Hints

- How are the critical numbers of a function related to the zeros of its derivative? - On which intervals is each graph increasing or decreasing? - What sign should the derivative have when the original function is increasing or decreasing? - Check both possible assignments.

Solution

1. The graph labeled \(f\) has a local maximum between \(x=-2\) and \(x=-1\), and a local minimum between \(x=1\) and \(x=2\). The graph labeled \(g\) is zero at those same x-coordinates. 2. The graph of \(f\) increases before the first critical number, decreases between the two critical numbers, and increases after the second critical number. Over those intervals, \(g\) is positive, negative, and positive, respectively. 3. Therefore, the values of \(g\) match the slopes of \(f\), so \(g=f'\).

Answer

The graph labeled \(f\) represents the function, and the graph labeled \(g\) represents its derivative. Thus, \(g=f'\).
53235512
Figures 1 and 2 show a function \(f\) and its derivative \(f'\), but the two figures are not labeled by role. a) Identify which figure is \(f\) and which is \(f'\). Justify your choice using the relationship between horizontal tangents of \(f\) and zeros of \(f'\). b) Find \(f(2)\). c) Find the slope of \(f\) at \(x=-1\). d) Give one value \(a\) for which \(f(a)=1\). e) Find all values \(b\) for which the slope of \(f\) is \(3\).
Figure for problem 532355

Hints

- First decide which graph could be the derivative by comparing zeros on one graph with horizontal tangents on the other. - Only after identifying the roles should you read function values and derivative values. - A requested tangent slope is a requested value of \(f'\).

Solution

1. Figure 1 is \(f\) and Figure 2 is \(f'\). The turning points of Figure 1 occur at the same inputs where Figure 2 crosses the x-axis, which is the required function-derivative relationship. 2. From Figure 1, \(f(2)=-1\). 3. The slope at \(x=-1\) is \(f'(-1)\). Figure 2 gives \(f'(-1)=-1.5\). 4. Figure 1 passes through \((0,1)\), so \(a=0\) works. 5. A slope of \(3\) means \(f'(b)=3\). Figure 2 has value \(3\) at \(b=-2\) and \(b=2\).

Answer

a) Figure 1 is \(f\); Figure 2 is \(f'\). b) \(f(2)=-1\) c) \(-1.5\) d) \(a=0\) e) \(b=-2\) and \(b=2\)
53235712
The figure shows two graphs labeled \(k_1\) and \(k_2\). One graph represents a function \(f\), and the other represents its derivative \(f'\). a) Explain mathematically which graph represents \(f\) and which represents \(f'\). b) Use the graph to determine: - \(f(2)\) - \(f'(2)\) - \(f(3)\) - \(f'(1)\)
Figure for problem 532357

Hints

- Compare the turning points of one graph with the zeros of the other. - A differentiable function has derivative \(0\) at a smooth local maximum or minimum. - Compare where one graph increases or decreases with the sign of the other graph. - After identifying the graphs, read each requested value from the correct one.

Solution

1. The graph labeled \(k_1\) has a local maximum at \(x=1\) and a local minimum at \(x=3\). The graph labeled \(k_2\) is zero at those same x-values. Also, \(k_1\) decreases on \((1, 3)\), where \(k_2\) is negative. Therefore, \(k_1\) represents \(f\) and \(k_2\) represents \(f'\). 2. Reading the values from the graphs gives \(f(2)=2\), \(f'(2)=-1.5\), \(f(3)=1\), and \(f'(1)=0\).

Answer

a) \(k_1\) is the graph of \(f\), and \(k_2\) is the graph of \(f'\). b) \(f(2)=2\); \(f'(2)=-1.5\); \(f(3)=1\); \(f'(1)=0\)
53240212
The graph of \(f'\) is shown. Determine whether each statement about \(f\) is true or false. Justify your answers. a) The graph of \(f\) has a local minimum at \(x=-2\) and a local maximum at \(x=2\). b) The function \(f\) is strictly decreasing on \([-2,2]\). c) The graph of \(f\) has an inflection point at \(x=0\).
Figure for problem 532402

Hints

- Use the sign of \(f'\) for monotonicity and local extrema. - Use whether \(f'\) rises or falls for concavity. - Keep those two readings of the derivative graph separate.

Solution

1. Zeros and signs of \(f'\) determine critical points and monotonicity of \(f\), while local extrema of \(f'\) can indicate concavity changes of \(f\). 2. At \(x=-2\), \(f'\) changes from negative to positive, so \(f\) has a local minimum. At \(x=2\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. Statement a is true. 3. On \((-2,2)\), \(f'(x)>0\), so \(f\) is strictly increasing, not decreasing. Statement b is false. 4. The graph of \(f'\) has a local maximum at \(x=0\), so \(f'\) changes from increasing to decreasing. Therefore \(f\) changes from concave up to concave down at \(x=0\). Statement c is true.

Answer

a) True. b) False. c) True.
53243412
Panel a) shows the graphs labeled \(f_1\) and \(f_2\). Panel b) shows two possible derivative graphs, labeled \(p\) and \(q\). a) Match each function, \(f_1\) and \(f_2\), with its derivative, \(p\) or \(q\). Justify your choices. b) On the displayed interval \([-3.5, 3.5]\), find the intervals where \(f_1\) is strictly increasing and strictly decreasing.
Figure for problem 532434

Hints

- Match the zeros of a derivative with the horizontal tangents of its function. - Compare the sign of each possible derivative with where the function increases or decreases. - Use the critical \(x\)-values as interval endpoints.

Solution

1. The graph of \(f_1\) has a local maximum at \(x=-2\) and a local minimum at \(x=2\), so its derivative must be zero at those values. 2. Between the two critical numbers, \(f_1\) decreases, so its derivative must be negative there. Graph \(p\) is negative between its zeros, while graph \(q\) is positive. Therefore, \(f_1'=p\) and \(f_2'=q\). 3. Graph \(p\) is positive on \([-3.5, -2)\) and \((2, 3.5]\), and negative on \((-2, 2)\). Thus, \(f_1\) is strictly increasing on \([-3.5, -2]\) and \([2, 3.5]\), and strictly decreasing on \([-2, 2]\).

Answer

a) \(f_1 \rightarrow p\) and \(f_2 \rightarrow q\) b) Increasing on \([-3.5, -2]\) and \([2, 3.5]\); decreasing on \([-2, 2]\).
53252012
The two figures show the graphs of a function \(f\) and its derivative \(f'\). a) Use increasing and decreasing behavior to decide which figure shows \(f\) and which shows \(f'\). b) Find the interval on which \(f\) is strictly decreasing. How is this shown on the graph of \(f'\)? c) Use the derivative graph to determine the slope of the tangent to \(f\) at \(x = 0\).
Figure for problem 532520

Hints

- Compare where the function increases or decreases with the sign of the derivative. - The zeros of the derivative occur at horizontal tangents of the function. - The value \(f'(0)\) is the slope of \(f\) at \(x = 0\).

Solution

1. Figure 1 represents \(f\), and Figure 2 represents \(f'\). Figure 1 increases for \(x < -1\), decreases for \(-1 < x < 3\), and increases for \(x > 3\). Over the same intervals, Figure 2 is positive, negative, and positive. 2. The function \(f\) is strictly decreasing on \([-1, 3]\). The derivative graph is below the \(x\)-axis for \(-1 < x < 3\) and is zero at the endpoints. 3. The tangent slope at \(x = 0\) is \(f'(0)\). From Figure 2, \(f'(0) = -0.75\).

Answer

a) Figure 1 shows \(f\), and Figure 2 shows \(f'\). b) \([-1, 3]\); the graph of \(f'\) is below the \(x\)-axis between \(-1\) and \(3\). c) \(-0.75\)
53252612
The graph of \(f\) is shown. Answer each question about \(f'\) by reading and reasoning from the graph. a) Find the zeros of \(f'\). Briefly explain your method. b) Give the interval on which the graph of \(f'\) lies above the x-axis. c) Estimate \(f'(0)\) from the tangent slope at \(x=0\). Because this is a graph-based estimate, values from about \(1.3\) to \(1.7\) are acceptable.
Figure for problem 532526

Hints

- Look for inputs where the graph of \(f\) has horizontal tangents. - Relate increasing behavior of \(f\) to the sign of \(f'\). - For the estimate at \(x=0\), imagine a tangent line and use two convenient points to form a slope triangle.

Solution

1. The graph of \(f\) has a local minimum at \(x=-1\) and a local maximum at \(x=1\). Therefore, the zeros of \(f'\) are \(x=-1\) and \(x=1\). 2. The graph of \(f\) increases between the two extrema, so \(f'(x)>0\) for \(-1<x<1\). 3. At \(x=0\), a reasonable tangent estimate uses \((0,1)\) and approximately \((1,2.5)\), giving \(f'(0)\approx\frac{2.5-1}{1-0}=1.5\). Values from about \(1.3\) to \(1.7\) are consistent with the displayed graph.

Answer

a) \(x=-1\) and \(x=1\) b) \((-1,1)\) c) Approximately \(1.5\); estimates from about \(1.3\) to \(1.7\) are acceptable.
53254112
Figure 1 shows the graphs of two polynomial functions, \(f\) and \(g\). Figure 2 shows two derivative graphs, \(p\) and \(q\). a) Match each function, \(f\) and \(g\), with its derivative, \(p\) or \(q\). b) Justify your matches using features such as local maxima and minima, zeros, and increasing and decreasing behavior.
Figure for problem 532541

Hints

- Differentiation lowers the degree of a polynomial by one. - Match local extrema of a function with zeros of its derivative. - Compare where each function increases or decreases with the sign of each derivative graph.

Solution

1. The graph of \(f\) has a local maximum at \(x=-1\) and a local minimum at \(x=3\). Graph \(p\) is zero at those same values. It is negative between them, where \(f\) decreases, and positive outside them, where \(f\) increases. Therefore, \(f'=p\). 2. The graph of \(g\) has a local maximum at \(x=2\). Graph \(q\) is zero there, positive for \(x<2\), where \(g\) increases, and negative for \(x>2\), where \(g\) decreases. Therefore, \(g'=q\).

Answer

a) \(f\rightarrow p\) and \(g\rightarrow q\) b) The zeros and signs of \(p\) match the critical numbers and monotonicity of \(f\), while the zero and signs of \(q\) match those of \(g\).
53254712
The graph shown is the first derivative \(f'\) of a polynomial function \(f\) on \(-5\le x\le6\). a) Determine the intervals on which \(f\) is concave up and concave down. b) Find the x-coordinates of all inflection points of \(f\).
Figure for problem 532547

Hints

- Identify where the graph of \(f'\) is increasing and decreasing. - How does an increasing or decreasing first derivative determine concavity? - Inflection-point x-coordinates of \(f\) occur where the monotonicity of \(f'\) changes.

Solution

1. The function \(f\) is concave up where \(f'\) is increasing and concave down where \(f'\) is decreasing. 2. On the displayed interval, \(f'\) is increasing on \([-5, -1)\) and \((3, 6]\). Therefore, \(f\) is concave up on those intervals. 3. The graph of \(f'\) is decreasing on \((-1, 3)\). Therefore, \(f\) is concave down on that interval. 4. The monotonicity of \(f'\) changes at its local extrema, \(x=-1\) and \(x=3\). Thus these are the x-coordinates of the inflection points of \(f\).

Answer

a) Concave up on \([-5, -1)\) and \((3, 6]\); concave down on \((-1, 3)\). b) \(x=-1\) and \(x=3\)
53255212
The graph of a function \(f\) is shown. For each marked point \(A\), \(B\), \(C\), and \(D\), determine whether the function value \(f(x)\), first derivative \(f'(x)\), and second derivative \(f''(x)\) are positive, negative, or zero. Enter your results in the table. <table border="1" style="border-collapse: collapse; text-align: center; width: 100%; max-width: 500px; margin-top: 10px;"> <thead> <tr> <th style="padding: 5px 10px;">Point</th> <th style="padding: 5px 10px;">\(f(x)\)</th> <th style="padding: 5px 10px;">\(f'(x)\)</th> <th style="padding: 5px 10px;">\(f''(x)\)</th> </tr> </thead> <tbody> <tr> <td style="padding: 5px 10px;">\(A\)</td> <td style="padding: 5px 10px;">...</td> <td style="padding: 5px 10px;">...</td> <td style="padding: 5px 10px;">...</td> </tr> <tr> <td style="padding: 5px 10px;">\(B\)</td> <td style="padding: 5px 10px;">...</td> <td style="padding: 5px 10px;">...</td> <td style="padding: 5px 10px;">...</td> </tr> <tr> <td style="padding: 5px 10px;">\(C\)</td> <td style="padding: 5px 10px;">...</td> <td style="padding: 5px 10px;">...</td> <td style="padding: 5px 10px;">...</td> </tr> <tr> <td style="padding: 5px 10px;">\(D\)</td> <td style="padding: 5px 10px;">...</td> <td style="padding: 5px 10px;">...</td> <td style="padding: 5px 10px;">...</td> </tr> </tbody> </table>
Figure for problem 532552

Hints

- How does a point’s position relative to the x-axis determine the sign of \(f(x)\)? - What does the tangent slope tell you about the sign of \(f'(x)\)? - What is special about the tangent at a local maximum or minimum? - How does concavity determine the sign of \(f''(x)\)? - What happens to concavity at an inflection point?

Solution

1. Use each point’s position relative to the x-axis to determine the sign of \(f(x)\): \(f(x_A)<0\), \(f(x_B)>0\), \(f(x_C)>0\), and \(f(x_D)<0\). 2. Use the tangent slope to determine the sign of \(f'(x)\). The graph is increasing at \(A\), has a horizontal tangent at the local maximum \(B\), is decreasing at \(C\), and has a horizontal tangent at the local minimum \(D\). Therefore, \(f'(x_A)>0\), \(f'(x_B)=0\), \(f'(x_C)<0\), and \(f'(x_D)=0\). 3. Use concavity to determine the sign of \(f''(x)\). The graph is concave down at \(A\) and \(B\), changes concavity at \(C\), and is concave up at \(D\). Therefore, \(f''(x_A)<0\), \(f''(x_B)<0\), \(f''(x_C)=0\), and \(f''(x_D)>0\).

Answer

The completed table is: <table border="1" style="border-collapse: collapse; text-align: center; margin-top: 10px;"> <thead> <tr> <th style="padding: 5px 10px; background-color: #f2f2f2;">Point</th> <th style="padding: 5px 10px; background-color: #f2f2f2;">\(f(x)\)</th> <th style="padding: 5px 10px; background-color: #f2f2f2;">\(f'(x)\)</th> <th style="padding: 5px 10px; background-color: #f2f2f2;">\(f''(x)\)</th> </tr> </thead> <tbody> <tr> <td style="padding: 5px 10px; font-weight: bold;">\(A\)</td> <td style="padding: 5px 10px; color: red;">negative (\(<0\))</td> <td style="padding: 5px 10px; color: green;">positive (\(>0\))</td> <td style="padding: 5px 10px; color: red;">negative (\(<0\))</td> </tr> <tr> <td style="padding: 5px 10px; font-weight: bold;">\(B\)</td> <td style="padding: 5px 10px; color: green;">positive (\(>0\))</td> <td style="padding: 5px 10px;">zero (\(=0\))</td> <td style="padding: 5px 10px; color: red;">negative (\(<0\))</td> </tr> <tr> <td style="padding: 5px 10px; font-weight: bold;">\(C\)</td> <td style="padding: 5px 10px; color: green;">positive (\(>0\))</td> <td style="padding: 5px 10px; color: red;">negative (\(<0\))</td> <td style="padding: 5px 10px;">zero (\(=0\))</td> </tr> <tr> <td style="padding: 5px 10px; font-weight: bold;">\(D\)</td> <td style="padding: 5px 10px; color: red;">negative (\(<0\))</td> <td style="padding: 5px 10px;">zero (\(=0\))</td> <td style="padding: 5px 10px; color: green;">positive (\(>0\))</td> </tr> </tbody> </table>
53255612
The graph shown is the second derivative \(f''\) of a polynomial function \(f\) on \(-4\le x\le4\). a) Determine the intervals where \(f\) is concave up and concave down. b) Find the x-coordinates of the inflection points of \(f\) and justify your answer. c) Evaluate the statement: “The graph of the first derivative \(f'\) has a local extremum at \(x=0\).”
Figure for problem 532556

Hints

- How does the sign of the second derivative determine concavity? - An inflection point requires a change in the sign of the second derivative. - What condition must hold for the first derivative to have a local extremum?

Solution

1. The graph of \(f''\) is above the x-axis on \([-4, -2)\) and \((2, 4]\). Therefore, \(f\) is concave up on those intervals. It is below the x-axis on \((-2, 2)\), so \(f\) is concave down there. 2. At \(x=-2\) and \(x=2\), the second derivative is zero and changes sign. Therefore, these are the x-coordinates of the inflection points of \(f\). 3. The statement is false. A local extremum of \(f'\) at \(x=0\) would require \(f''(0)=0\). The graph shows \(f''(0)=-4\), so \(f'\) does not have a local extremum there.

Answer

a) Concave up on \([-4, -2)\) and \((2, 4]\); concave down on \((-2, 2)\). b) \(x=-2\) and \(x=2\) c) False, because \(f''(0)=-4\ne0\).
53260312
The panel labeled \(f'\) shows the graph of \(f'\). Panels 1, 2, and 3 show three candidate graphs for \(f\). a) Which candidate represents \(f\)? b) Explain why the other two candidates cannot represent \(f\).
Figure for problem 532603

Hints

- Zeros of the derivative correspond to critical numbers of the original function. - The sign of the derivative determines increasing and decreasing intervals. - Check both the critical numbers and the direction of each sign change.

Solution

1. The derivative graph has zeros at \(x=1\) and \(x=3\), so \(f\) must have critical numbers at those x-values. 2. Candidate 2 has extrema at \(x=0\) and \(x=2\), so it cannot be \(f\). 3. For \(x<1\), \(f'(x)>0\), so \(f\) must be increasing. Candidate 1 increases before \(x=1\) and has a local maximum there because \(f'\) changes from positive to negative. 4. Candidate 3 decreases before \(x=1\), which contradicts \(f'(x)>0\). Therefore, candidate 1 represents \(f\).

Answer

a) Candidate 1. b) Candidate 2 has critical numbers at the wrong x-values, and candidate 3 has the wrong monotonicity.
53260412
The graph of \(g'\) is shown. a) Use the graph to identify the x-coordinates and types of the local extrema of \(g\). b) A candidate function is \(g(x)=-\frac{1}{18}x^3+1.5x+1\). Differentiate it to verify that its derivative matches the displayed graph. c) Find the coordinates of the local maximum and local minimum of this \(g\), and confirm that they agree with part a).
Figure for problem 532604

Hints

- Use derivative zeros and sign changes for part a). - Verify the candidate function by differentiating it, not by reversing differentiation. - Substitute the critical x-values into the verified function to get coordinates.

Solution

1. The zeros of \(g'\) are \(x=-3\) and \(x=3\). At \(x=-3\), \(g'\) changes from negative to positive, so \(g\) has a local minimum. At \(x=3\), \(g'\) changes from positive to negative, so \(g\) has a local maximum. 2. Differentiating \(g(x)=-\frac{1}{18}x^3+1.5x+1\) gives \(g'(x)=-\frac16x^2+1.5\), which matches the displayed derivative. 3. \(g(-3)=-2\) and \(g(3)=4\). Therefore, the local minimum is \((-3,-2)\), and the local maximum is \((3,4)\).

Answer

a) Local minimum at \(x=-3\); local maximum at \(x=3\). b) \(g'(x)=-\frac16x^2+1.5\), matching the graph. c) Local minimum \((-3,-2)\); local maximum \((3,4)\).
53266812
The graph shows two curves labeled \(p\) and \(q\). One is a function \(f\), and the other is its derivative \(f'\). a) Identify which curve is \(f\) and which is \(f'\). Justify your choice by comparing the minimum of one curve with a zero of the other. b) Use the correctly identified derivative curve to find the slope of the tangent to \(f\) at \(x=0\): \(-2\), \(-1\), or \(0\). c) Find the \(x\)-values where \(f(x)=f'(x)\).
Figure for problem 532668

Hints

- A smooth minimum of \(f\) must occur where \(f'\) is zero. - Identify the roles of the two curves before reading the requested slope. - Equal function and derivative values occur where the two curves intersect.

Solution

1. Curve \(p\) is \(f\), and curve \(q\) is \(f'\). Curve \(p\) has a minimum at \(x=1\), while curve \(q\) has value \(0\) there, as a derivative must at a smooth minimum. 2. At \(x=0\), curve \(q\) has value \(-1\), so the tangent slope is \(f'(0)=-1\). 3. The function and derivative have equal values where curves \(p\) and \(q\) intersect. The intersections occur at \(x=1\) and \(x=3\).

Answer

a) \(p=f\) and \(q=f'\) b) \(-1\) c) \(x=1\) and \(x=3\)
53277012
The three panels show the graphs of a function \(f\), its first derivative \(f'\), and its second derivative \(f''\). Match \(f\), \(f'\), and \(f''\) with graphs a, b, and c. Justify your matches.
Figure for problem 532770

Hints

- At a local maximum or minimum, the first derivative is zero. - Compare where one graph increases or decreases with where a candidate derivative is positive or negative. - Build a two-step derivative chain among the three graphs.

Solution

1. Graph b has a local maximum at \(x=0\). Its derivative must be zero there and change from positive to negative. Graph c has exactly that behavior, so graph c is the derivative of graph b. 2. Graph c has a local minimum at \(x=1\) and a local maximum at \(x=3\). Its derivative must have zeros at \(x=1\) and \(x=3\). Graph a has those zeros and its sign matches the increasing/decreasing behavior of graph c. Therefore, graph a is the derivative of graph c. 3. The derivative chain is graph b \(\to\) graph c \(\to\) graph a. Hence graph b is \(f\), graph c is \(f'\), and graph a is \(f''\).

Answer

Graph a: \(f''\); graph b: \(f\); graph c: \(f'\).
53368712
The graph shows the functions labeled \(f\) and \(g\). Use the local extremum of \(f\) and the zeros of \(g\) to explain why \(g\) cannot be the derivative of \(f\).
Figure for problem 533687

Hints

- What must the derivative equal at a smooth local maximum or minimum? - Compare the \(x\)-coordinate of the vertex of \(f\) with the zeros of \(g\).

Solution

1. The graph of \(f\) has a local minimum at \(x=0\). 2. If \(g=f'\), then \(g(0)\) would have to equal \(0\), because the tangent to \(f\) is horizontal at a smooth local minimum. 3. The graph shows \(g(0)=1\), not \(0\). Therefore, \(g\) cannot be the derivative of \(f\).

Answer

The function \(f\) has a local minimum at \(x = 0\), so its derivative must be \(0\) there. Since \(g(0) = 1\), \(g\) cannot equal \(f'\).
53368812
The graphs show the functions labeled \(f\) and \(g\). Explain why \(f\) cannot be the derivative of \(g\). Focus on the behavior of \(g\) for \(x>0\).
Figure for problem 533688

Hints

- What sign must a derivative have where its function is decreasing? - Compare that sign with the graph of \(f\) for \(x>0\).

Solution

1. For \(x>0\), the graph of \(g\) is strictly decreasing. 2. If \(f=g'\), then \(f(x)\) would have to be negative wherever \(g\) is decreasing. 3. For \(x>0\), the graph of \(f\) is above the x-axis, so \(f(x)>0\). This contradicts the required sign of the derivative. Therefore, \(f\) cannot be the derivative of \(g\).

Answer

For \(x > 0\), \(g\) is decreasing, so its derivative must be negative. Since \(f(x) > 0\) in that region, \(f\) cannot equal \(g'\).
53379912
The graph shown is the derivative \(f'\) of a function \(f\). Determine whether each statement is true or false, and briefly justify your answer. a) On the displayed domain, \(f\) is decreasing for \(-2<x\le5\). b) The function \(f\) has a local extremum at \(x=3\). c) The function \(f\) has an inflection point at \(x=3\). d) The slope of \(f\) at \(x=1\) is positive.
Figure for problem 533799

Hints

- Use the sign of \(f'\) to determine monotonicity. - A local extremum of \(f\) requires a sign change in \(f'\). - Local extrema of \(f'\) correspond to inflection points of \(f\). - The slope of \(f\) at a point is the value of \(f'\) there.

Solution

1. Statement a is true. For \(-2<x\le5\), \(f'(x)\le0\), and the derivative is zero only at \(x=3\). Therefore, \(f\) is strictly decreasing there. 2. Statement b is false. At \(x=3\), \(f'\) does not change sign, so \(f\) has no local extremum. 3. Statement c is true. The graph of \(f'\) has a local maximum at \(x=3\), so the concavity of \(f\) changes there. 4. Statement d is false. The graph shows \(f'(1)<0\), so the slope of \(f\) at \(x=1\) is negative.

Answer

a) True b) False c) True d) False
53381612
The graph shows the derivative \(f'\) of a function \(f\). Answer the following questions about \(f\): 1. How many local extrema does \(f\) have in the displayed interval? 2. At which \(x\)-value does \(f\) have a local minimum? 3. How many inflection points does the graph of \(f\) have?
Figure for problem 533816

Hints

- Count the zeros of \(f'\) where the sign changes. - A change from negative to positive gives a local minimum. - Count the local extrema of \(f'\) to determine the number of inflection points of \(f\).

Solution

1. Local extrema of \(f\) occur where \(f'\) is zero and changes sign. This happens at \(x = -2\), \(x = 0\), and \(x = 2\), so \(f\) has three local extrema. 2. At \(x = -2\), \(f'\) changes from positive to negative, giving a local maximum. At \(x = 0\), it changes from negative to positive, giving a local minimum. At \(x = 2\), it changes from positive to negative, giving a local maximum. 3. Inflection points of \(f\) occur where \(f'\) has local extrema. The derivative graph has exactly two local extrema in the displayed interval, so \(f\) has two inflection points.

Answer

1. Three local extrema 2. A local minimum at \(x = 0\) 3. Two inflection points
53387312
The figure shows graphs labeled \(A\) and \(B\). One graph represents a function \(f\), and the other represents its derivative \(f'\). Use two characteristic features of the graphs to identify each one.
Figure for problem 533873

Hints

- Compare the local extremum of one graph with the zero of the other. - Compare increasing and decreasing intervals with the sign of the possible derivative.

Solution

1. Graph \(A\) has a local maximum at \(x=0\), and graph \(B\) is zero at \(x=0\). This matches the fact that the derivative is zero at a smooth local extremum. 2. For \(x>0\), graph \(A\) decreases, and graph \(B\) is below the x-axis. This matches the fact that a derivative is negative where its function decreases. 3. Therefore, graph \(A\) represents \(f\), and graph \(B\) represents \(f'\).

Answer

Graph A represents \(f\), and graph B represents \(f'\). The zero of graph B matches the local maximum of graph A, and the sign of graph B matches where graph A increases or decreases.
53389912
The graph of a function \(f\) is shown; no algebraic formula for \(f\) is given. Use only the changing steepness of the graph to describe the graph of \(f'\). State whether \(f'\) is positive or negative, whether it increases or decreases from left to right, whether it has any zeros, and what value \(f'(x)\) approaches as \(x\to-\infty\).
Figure for problem 533899

Hints

- Use only the graph; no function formula is available. - Determine the sign of the tangent slopes along the curve. - Compare the steepness on the left and right sides of the graph. - Consider what happens to tangent slopes where the graph becomes nearly horizontal.

Solution

1. The graph of \(f\) rises everywhere, so every visible tangent slope is positive. Thus \(f'(x)>0\) and the derivative has no zeros. 2. The graph becomes steeper from left to right, so its tangent slopes increase. Therefore, \(f'\) is increasing. 3. Far to the left, the graph becomes nearly horizontal, so the tangent slopes approach \(0\) from above. Hence \(f'(x)\to0\) as \(x\to-\infty\).

Answer

The graph of \(f'\) stays above the x-axis, increases from left to right, has no zeros, and approaches \(0\) from above as \(x\to-\infty\).
53390012
Let \(f(x)=4(0.75)^x\). Analyze the concavity of the graph of \(f\). What does the concavity imply about the monotonicity of the derivative \(f'\)? Describe the graph of \(f'\) qualitatively.

Hints

- Differentiate the exponential function twice. - Use the sign of the second derivative to determine concavity. - Use the sign of the second derivative to determine whether the first derivative increases or decreases.

Solution

1. The first derivative is \(f'(x)=4\ln(0.75)(0.75)^x\). Since \(\ln(0.75)<0\), the function \(f\) is strictly decreasing and \(f'(x)<0\) for every \(x\). 2. The second derivative is \(f''(x)=4[\ln(0.75)]^2(0.75)^x>0\). Therefore, the graph of \(f\) is concave up. 3. Because \(f''(x)>0\), the derivative \(f'\) is strictly increasing. Its graph remains below the x-axis, satisfies \(f'(x)\to-\infty\) as \(x\to-\infty\), and approaches the x-axis from below as \(x\to\infty\).

Answer

The graph of \(f\) is concave up. The derivative \(f'\) is strictly increasing, remains negative, satisfies \(f'(x)\to-\infty\) as \(x\to-\infty\), and approaches \(0\) from below as \(x\to\infty\).
53391712
The figure shows three function graphs, A, B, and C, and three possible derivative graphs, 1, 2, and 3. Match each function graph with its derivative graph. Justify your choices using slope, local extrema, or stationary inflection points.
Figure for problem 533917

Hints

- Match horizontal tangents with zeros of the derivative. - Compare where each function increases or decreases with the sign of its derivative. - A stationary inflection point gives a derivative that touches the \(x\)-axis without changing sign.

Solution

1. Graph A is an upward-opening parabola with vertex at the origin. Its derivative is an increasing line through the origin, so A matches 3. 2. Graph B is a downward-opening parabola with vertex \((0, 3)\). Its derivative is a decreasing line through the origin, so B matches 2. 3. Graph C is cubic with a stationary inflection point at the origin. Its derivative is nonnegative and equals \(0\) at the origin, so it is an upward-opening parabola with vertex at the origin. Thus, C matches 1.

Answer

A \(\rightarrow\) 3; B \(\rightarrow\) 2; C \(\rightarrow\) 1.
53391812
Which derivative graph, 1, 2, or 3, matches each function graph, A, B, or C? Justify your matches using local extrema and intervals of increase and decrease.
Figure for problem 533918

Hints

- Match local extrema with zeros of the derivative. - Compare where each function increases or decreases with the sign of the derivative. - Recall the derivative of \(\sin x\).

Solution

1. Graph A is a parabola with a minimum at \(x=2\). Its derivative must change from negative to positive at \(x=2\), so A matches graph 1. 2. Graph B is \(\sin x\). Its derivative is \(\cos x\), whose graph is 2. 3. Graph C has a local minimum at \(x=-1\) and a local maximum at \(x=1\). It increases between those values and decreases outside them. Its derivative must be positive on \((-1,1)\), negative outside, and zero at \(x=\pm1\). Thus, C matches graph 3.

Answer

A \(\rightarrow\) 1; B \(\rightarrow\) 2; C \(\rightarrow\) 3.
53397512
The graph shown is the derivative \(g'\) of a function \(g\). a) Find the x-coordinates of the inflection points of \(g\). Briefly explain your method. b) At \(x=2\), does \(g\) have a local extremum or a stationary inflection point? Justify your answer using the graph of \(g'\).
Figure for problem 533975

Hints

- Local extrema of \(g'\) correspond to inflection points of \(g\). - A zero of \(g'\) without a sign change does not produce a local extremum of \(g\). - Does \(g'\) change sign at \(x=2\)? - What combines a change in concavity with a horizontal tangent?

Solution

1. Inflection points of \(g\) occur where the graph of \(g'\) has local extrema. 2. The graph of \(g'\) has a local maximum at \(x=0\) and a local minimum at \(x=2\). Therefore, \(g\) has inflection points at \(x=0\) and \(x=2\). 3. At \(x=2\), \(g'(2)=0\), but \(g'\) only touches the x-axis and does not change sign. Thus \(g\) has no local extremum there. Because \(g\) changes concavity and has a horizontal tangent, it has a stationary inflection point at \(x=2\).

Answer

a) \(x=0\) and \(x=2\) b) A stationary inflection point occurs at \(x=2\).
53401012
The graph shown is the first derivative \(f'\) of a function \(f\). Find the x-coordinates of the inflection points of \(f\). Then determine the intervals in the displayed window where \(f\) is concave up and concave down. Justify your answers using the graph of \(f'\).
Figure for problem 534010

Hints

- Local extrema of \(f'\) correspond to inflection points of \(f\). - Increasing \(f'\) means \(f\) is concave up. - Decreasing \(f'\) means \(f\) is concave down.

Solution

1. The graph of \(f'\) has local extrema at \(x=-2\) and \(x=2\). Therefore, \(f\) has inflection points at those x-values. 2. The displayed x-range is \([-4, 5]\). The graph of \(f'\) is increasing on \([-4, -2)\) and \((2, 5]\), so \(f\) is concave up there. 3. The graph of \(f'\) is decreasing on \((-2, 2)\), so \(f\) is concave down there.

Answer

Inflection-point x-coordinates: \(x=-2\) and \(x=2\). Concave up on \([-4,-2)\) and \((2,5]\); concave down on \((-2,2)\).
53420112
The figure shows two functions, \(f\) and \(g\). Explain mathematically why neither \(g\) can be the derivative of \(f\) nor \(f\) can be the derivative of \(g\). Use features such as zeros, local extrema, or monotonicity.
Figure for problem 534201

Hints

- What must a derivative equal at a smooth local extremum? - What type of function is the derivative of a line? - Compare the zeros of one graph with the horizontal tangents of the other.

Solution

1. The graph of \(f\) has a local minimum at \(x = 2\). If \(g = f'\), then \(g(2)\) would have to be \(0\). Instead, the graph shows \(g(2) > 0\), so \(g\) is not the derivative of \(f\). 2. The graph of \(g\) is a line with constant slope \(-0.5\). Therefore, its derivative is the constant function \(-0.5\). Since \(f\) is a parabola, \(f\) cannot be the derivative of \(g\).

Answer

\(g\) is not the derivative of \(f\) because \(f\) has a local minimum at \(x = 2\), but \(g(2) > 0\). \(f\) is not the derivative of \(g\) because the derivative of the line \(g\) must be a constant function, not a parabola.
53422812
The graph of a quartic polynomial \(f\) is shown. Decide whether each statement is true or false. (1) The graph is symmetric about the y-axis. (2) The derivative \(f'\) has a zero at \(x=0\). (3) For \(2<x\le3.5\), the graph has positive slope. (4) The function has exactly four zeros on \([-3, 3]\).
Figure for problem 534228

Hints

- Check for a vertical line of symmetry. - A local maximum or minimum has a horizontal tangent. - Determine whether the graph rises or falls on the stated interval. - Count all x-intercepts, including points where the graph only touches the axis.

Solution

1. The graph is symmetric about the y-axis, so (1) is true. 2. The graph has a local minimum at \(x=0\), so \(f'(0)=0\). Thus, (2) is true. 3. On \(2<x\le3.5\), the graph is decreasing, so its slope is negative. Thus, (3) is false. 4. The graph has four x-intercepts on \([-3, 3]\), so (4) is true.

Answer

(1) True (2) True (3) False (4) True
53427712
The graph shown is the second derivative \(f''\) of a polynomial function \(f\). Find the x-coordinates of all inflection points of \(f\), and state the intervals in the displayed window where \(f\) is concave down.
Figure for problem 534277

Hints

- What does the sign of the second derivative tell you about concavity? - Look for zeros of \(f''\) where the graph crosses the x-axis. - Concave-down intervals occur where \(f''\) is negative.

Solution

1. Inflection points occur where \(f''\) is zero and changes sign. The graph crosses the x-axis at \(x=-4\), \(x=0\), and \(x=4\), so these are the x-coordinates of the inflection points. 2. On the displayed interval \([-6,6]\), \(f''(x)<0\) on \([-6,-4)\) and \((0,4)\). Therefore, \(f\) is concave down on those intervals.

Answer

Inflection-point x-coordinates: \(x=-4\), \(x=0\), and \(x=4\). Concave down on \([-6,-4)\) and \((0,4)\).
53429912
The graph of \(f\) has three marked points. Determine the signs of \(f(x)\), \(f'(x)\), and \(f''(x)\) at \(A\), \(B\), and \(C\). What special name is given to point \(B\)? Explain using your results for \(f'(x)\) and \(f''(x)\).
Figure for problem 534299

Hints

- Use the point’s position relative to the x-axis for the sign of \(f(x)\). - Use the tangent slope for the sign of \(f'(x)\). - Look for a change in concavity at \(B\).

Solution

1. At \(A\), the graph is on the x-axis, increasing, and concave down. Therefore, \(f(x)=0\), \(f'(x)>0\), and \(f''(x)<0\). 2. At \(B\), the graph is above the x-axis and has a horizontal tangent. It also changes concavity there. Therefore, \(f(x)>0\), \(f'(x)=0\), and \(f''(x)=0\). A point that is both an inflection point and has a horizontal tangent is a stationary inflection point. 3. At \(C\), the graph is above the x-axis, increasing, and concave up. Therefore, \(f(x)>0\), \(f'(x)>0\), and \(f''(x)>0\).

Answer

Point \(A\): \(f(x)=0\), \(f'(x)>0\), \(f''(x)<0\) Point \(B\): \(f(x)>0\), \(f'(x)=0\), \(f''(x)=0\); \(B\) is a stationary inflection point. Point \(C\): \(f(x)>0\), \(f'(x)>0\), \(f''(x)>0\)
53430112
The graph shown is the second derivative \(f''\) of a polynomial function \(f\). Determine whether each statement is true or false, and justify your answer. a) The graph of \(f\) is concave up for \(1<x<3\). b) The function \(f\) has an inflection point at \(x=2\). c) The first derivative \(f'\) is strictly increasing on \([0, 2]\). d) The graph of \(f\) has an inflection point at \(x=3\).
Figure for problem 534301

Hints

- Confirm that the displayed graph represents \(f''\), not \(f\) or \(f'\). - Use the sign of \(f''\) to determine concavity. - An inflection point requires a sign change in \(f''\). - Use \(f''\) as the derivative of \(f'\) to analyze the monotonicity of \(f'\).

Solution

1. Statement a is true. On \((1,3)\), \(f''(x)>0\), so \(f\) is concave up. 2. Statement b is false. The graph shows \(f''(2)=1\ne0\), so \(x=2\) is not the x-coordinate of an inflection point. 3. Statement c is false. The derivative of \(f'\) is \(f''\). On \([0,2]\), \(f''\) is negative for \(0\le x<1\) and positive for \(1<x\le2\), so \(f'\) is not increasing throughout the interval. 4. Statement d is true. At \(x=3\), \(f''\) changes from positive to negative, so \(f\) changes concavity.

Answer

a) True b) False c) False d) True
53430512
The graph shows \(f\) on \([-3, 3]\). a) Estimate every \(x\)-value where \(f'(x)=0\). b) Determine the sign of \(f''(0)\).
Figure for problem 534305

Hints

- Look for points with horizontal tangents. - Inspect the graph's concavity near \(x=0\).

Solution

1. Horizontal tangents occur at the visible local extrema. From the graph, they occur at approximately \(x=-2.2\), \(x=0\), and \(x=2.2\). 2. Near \(x=0\), the graph is concave down. Therefore, \(f''(0)<0\).

Answer

a) \(x\approx-2.2\), \(x=0\), and \(x\approx2.2\) b) \(f''(0)<0\)
53430612
Point \(P\) is marked on the graph of the cubic function \(f\). Determine the value of \(f'(-2)\) and the sign of \(f''(-2)\).
Figure for problem 534306

Hints

- A smooth local extremum has a horizontal tangent. - Inspect the graph's concavity at \(P\) to determine the sign of the second derivative.

Solution

1. The marked point \(P\) at \(x=-2\) is a local maximum, so the tangent is horizontal. Therefore, \(f'(-2)=0\). 2. The graph is concave down at \(x=-2\), so \(f''(-2)<0\).

Answer

\(f'(-2)=0\) and \(f''(-2)<0\)
53431312
The graph shown is the second derivative \(f''\) of a polynomial function \(f\) on \(-2\le x\le5\). Determine whether each statement is true or false. a) The graph of \(f\) is concave down for \(-1<x<3\). b) The first derivative \(f'\) is strictly decreasing for \(3<x\le5\). c) The function \(f\) has an inflection point at \(x=1\). d) If \(f'(0)=0\), then \(f\) has a local maximum at \(x=0\).
Figure for problem 534313

Hints

- Use the sign of \(f''\) to determine concavity. - Use \(f''\) as the derivative of \(f'\) to determine whether \(f'\) increases or decreases. - For a polynomial, what must happen to \(f''\) at an inflection point? - Apply the second derivative test in part d.

Solution

1. Statement a is true because \(f''(x)<0\) for \(-1<x<3\). 2. Statement b is false because \(f''(x)>0\) for \(3<x\le5\), so \(f'\) is increasing there. 3. Statement c is false because \(f''(1)\ne0\). 4. Statement d is true. If \(f'(0)=0\) and \(f''(0)<0\), the second derivative test gives a local maximum at \(x=0\).

Answer

a) True b) False c) False d) True
53435512
A function \(g\), defined for all real numbers, has exactly two inflection points on \([-5, 5]\). Decide which graph—I, II, or III—could represent \(g''\). Justify your choice and briefly explain why the other graphs cannot represent \(g''\).
Figure for problem 534355

Hints

- What must the second derivative do at an inflection point? - Is a zero of the second derivative alone enough to guarantee an inflection point? - Count the zeros with sign changes in each graph. - Distinguish between crossing and merely touching the x-axis.

Solution

1. Inflection points of \(g\) occur where \(g''\) changes sign. 2. In graph III, the curve touches the x-axis at \(x=-3\) and \(x=3\), but it remains negative on both sides of each zero. There are no sign changes, so this graph would produce no inflection points. 3. Graph II crosses the x-axis at \(x=-3\), \(x=0\), and \(x=3\). Each crossing is a sign change, so this graph would produce three inflection points. 4. Graph I crosses the x-axis only at \(x=-3\) and \(x=3\), and it changes sign at both zeros. Therefore, graph I produces exactly two inflection points.

Answer

Graph I. It has exactly two zeros with sign changes, at \(x=-3\) and \(x=3\). Graph II has three such zeros, while graph III has no sign changes at its zeros.
53439112
The displays show the graphs of two functions, \(f\) and \(g\), and two possible derivative graphs, \(h_1\) and \(h_2\). Match each function with its derivative graph. Justify your choices by comparing critical points, zeros, and intervals where the functions increase or decrease.
Figure for problem 534391

Hints

- Local maxima and minima of a function correspond to zeros of its derivative. - Compare where each function increases or decreases with where each derivative is positive or negative. - Check all zeros of each possible derivative graph. - Verify that the derivative sign agrees with the slope of the function graph.

Solution

1. The graph of \(f\) has two symmetric local minima and a local maximum at \(x=0\). Its derivative must be zero at those three \(x\)-coordinates. Graph \(h_2\) has zeros at the same locations, with signs that match the increasing and decreasing behavior of \(f\). Therefore, \(f\) matches \(h_2\). 2. The graph of \(g\) has two symmetric local maxima and a local minimum at \(x=0\). Graph \(h_1\) has zeros at the same three \(x\)-coordinates, with signs that match the increasing and decreasing behavior of \(g\). Therefore, \(g\) matches \(h_1\).

Answer

\(f\) matches \(h_2\), and \(g\) matches \(h_1\).
53441612
The graph of \(f'\) is shown. Determine whether each statement about \(f\) is true or false. Give a brief justification. (1) \(f\) is strictly increasing on \([1,4]\). (2) \(f\) has a local maximum at \(x=5\). (3) The graph of \(f\) is concave down on \([0,2]\). (4) The tangent to the graph of \(f\) at \(x=3\) has slope \(2\).
Figure for problem 534416

Hints

- The sign of \(f'\) determines increasing and decreasing behavior. - A sign change of \(f'\) classifies a local extremum. - Whether \(f'\) is increasing or decreasing determines concavity. - The y-value of the derivative graph is the tangent slope of \(f\).

Solution

1. True. The graph shows \(f'>0\) on \((1,4)\), so \(f\) is strictly increasing there. 2. True. At \(x=5\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. 3. False. The derivative graph is increasing on \((0,2)\), so \(f\) is concave up there. 4. True. The tangent slope is \(f'(3)=2\).

Answer

(1) True. (2) True. (3) False. (4) True.
53442012
Graphs (1) and (2) are shown on \([0,2\pi]\). One graph represents a function \(f\), and the other represents its derivative \(f'\). Determine which graph is which and justify your answer.
Figure for problem 534420

Hints

- Zeros of a derivative correspond to horizontal tangents of the original function. - A positive derivative means the original function is increasing; a negative derivative means it is decreasing. - Compare both relationships at the quarter-period points.

Solution

1. Graph (1) has zeros at \(x=\frac{\pi}{2}\) and \(x=\frac{3\pi}{2}\). Graph (2) has a local maximum and a local minimum at those same x-values, as an original function should when its derivative is zero and changes sign. 2. Graph (1) is positive on \((0,\frac{\pi}{2})\), and graph (2) is increasing there. Graph (1) is negative on \((\frac{\pi}{2},\frac{3\pi}{2})\), and graph (2) is decreasing there. 3. Therefore, graph (1) is \(f'\), and graph (2) is \(f\).

Answer

Graph (1) is \(f'\); graph (2) is \(f\).
53442112
Graphs (1) and (2) represent a function \(f\) and its derivative \(f'\). Determine which graph represents each. Justify your answer by comparing function values with slopes.
Figure for problem 534421

Hints

- Compare the y-value of one graph with the slope of the other at the same x-value. - Check whether the sign of the candidate derivative matches the direction of change of the candidate original function. - Use more than one point or interval to confirm the match.

Solution

1. If graph (2) is \(f'\), its value at each x-value must equal the slope of graph (1). 2. At \(x=0\), graph (2) has value \(0.5\). Graph (1) has a positive slope of \(0.5\) there. 3. Across the displayed interval, graph (2) stays positive while graph (1) is increasing, and the changing values of graph (2) agree with the changing steepness of graph (1). Therefore, graph (1) is \(f\), and graph (2) is \(f'\).

Answer

Graph (1) is \(f\); graph (2) is \(f'\).
53442212
The two graphs shown on \(-0.8\le x\le5\) represent a function \(f\) and its derivative \(f'\). Determine which graph represents \(f\) and which represents \(f'\). Justify your answer using increasing/decreasing behavior and concavity.
Figure for problem 534422

Hints

- Compare the sign of one graph with whether the other graph rises or falls. - Compare whether the candidate derivative is increasing or decreasing with the concavity of the other graph. - Use the displayed formulas only after the graphical relationships are consistent.

Solution

1. Graph (1) is positive throughout the displayed interval, while graph (2) is increasing. Thus graph (1) can represent the derivative of graph (2). 2. Graph (1) decreases as \(x\) increases. Therefore, if graph (1) is \(f'\), then \(f''<0\), so graph (2) should be concave down. It is. 3. Algebraically, the derivative of \(\ln(x+1)\) is \(\frac{1}{x+1}\), confirming the relationship. 4. Therefore, graph (2) is \(f\), and graph (1) is \(f'\).

Answer

Graph (2) is \(f\), and graph (1) is \(f'\).
53443312
The graph of \(f'\) is shown on \([-4,4]\). a) Determine the open intervals on which \(f\) is increasing and decreasing. b) Find the \(x\)-coordinates of all local extrema of \(f\) and classify each. c) Determine the concavity intervals of \(f\) and the \(x\)-coordinate of its inflection point.
Figure for problem 534433

Hints

- Use where the derivative graph lies above or below the x-axis. - At each zero of the derivative, compare its signs on the two sides. - For concavity, focus on whether the derivative graph is decreasing or increasing.

Solution

1. Here \(f'(x)=x^2-4\). It is positive on \((-4,-2)\) and \((2,4)\), and negative on \((-2,2)\). Thus \(f\) increases on \((-4,-2)\) and \((2,4)\), and decreases on \((-2,2)\). 2. At \(x=-2\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. At \(x=2\), \(f'\) changes from negative to positive, so \(f\) has a local minimum. 3. Since \(f''(x)=2x\), \(f''<0\) for \(x<0\) and \(f''>0\) for \(x>0\). Therefore, \(f\) is concave down on \((-4,0)\), concave up on \((0,4)\), and has an inflection point at \(x=0\).

Answer

a) Increasing on \((-4,-2)\) and \((2,4)\); decreasing on \((-2,2)\) b) Local maximum at \(x=-2\); local minimum at \(x=2\) c) Concave down on \((-4,0)\); concave up on \((0,4)\); inflection point at \(x=0\)
53458112
The graph shows two curves labeled \(p\) and \(q\). One is a function \(f\), and the other is its derivative \(f'\). a) Identify which curve is \(f\) and which is \(f'\). Justify your choice from how the slope of the increasing curve changes as \(x\) increases. b) Find the slope of the tangent to \(f\) at \(x=1\) and at \(x=4\). c) At what x-value do \(f(x)\) and \(f'(x)\) have the same value?
Figure for problem 534581

Hints

- Decide which curve could represent tangent slopes of the other curve. - An increasing function has positive derivative values; if it becomes less steep, those derivative values should decrease. - After identifying \(f'\), read its y-values at the requested inputs.

Solution

1. Curve \(p\) is \(f\), and curve \(q\) is \(f'\). Curve \(p\) is increasing but becomes less steep, so its derivative should stay positive while decreasing; curve \(q\) has exactly that behavior. 2. From curve \(q\), \(f'(1)=0.5\) and \(f'(4)=0.25\). 3. The function and derivative have the same value where curves \(p\) and \(q\) intersect, which occurs at \(x=0.5\).

Answer

a) \(p=f\) and \(q=f'\) b) At \(x=1\), the slope is \(0.5\); at \(x=4\), the slope is \(0.25\). c) \(x=0.5\)
53460712
Match each function to Graph A, B, or C. Justify each match using end behavior and the locations of extrema or intercepts. \(g_1(x)=4xe^{-x}\) \(g_2(x)=e^x-x-1\) \(g_3(x)=2-e^{0.5x}\)
Figure for problem 534607

Hints

- Identify which graph approaches the x-axis for large positive \(x\). - Compare behavior as \(x\to-\infty\). - Use zeros and y-intercepts to distinguish the functions. - Differentiate when an extremum is a useful identifying feature.

Solution

1. For \(g_1(x)=4xe^{-x}\), the graph has a zero at \(x=0\), approaches \(0\) as \(x\to\infty\), and approaches \(-\infty\) as \(x\to-\infty\). Also, \(g_1'(x)=4(1-x)e^{-x}\), so it has a maximum at \(x=1\), with value \(4/e\approx1.47\). This matches Graph A. 2. For \(g_2(x)=e^x-x-1\), \(g_2(0)=0\) and \(g_2'(x)=e^x-1\), which changes from negative to positive at \(x=0\). Thus, \((0, 0)\) is a minimum. The function approaches \(\infty\) in both directions. This matches Graph B. 3. For \(g_3(x)=2-e^{0.5x}\), the graph approaches the horizontal asymptote \(y=2\) as \(x\to-\infty\), has y-intercept \(1\), and approaches \(-\infty\) as \(x\to\infty\). This matches Graph C.

Answer

Graph A: \(g_1(x)=4xe^{-x}\); Graph B: \(g_2(x)=e^x-x-1\); Graph C: \(g_3(x)=2-e^{0.5x}\)
53465312
The graph of a cubic function \(f\) is shown. a) Find all x-values where \(f'(x)=0\). b) On what open interval is \(f'(x)<0\)? c) On what open interval in the displayed domain is \(f''(x)>0\)? d) Classify the local extrema of \(f\). e) Give the x-coordinate of the inflection point of \(f\).
Figure for problem 534653

Hints

- Horizontal tangents reveal zeros of the first derivative. - Read the sign of \(f'\) from whether the graph rises or falls. - Read the sign of \(f''\) from the graph's concavity. - A change in concavity identifies an inflection point.

Solution

1. Zeros of \(f'\) occur where the graph of \(f\) has horizontal tangents. The graph has horizontal tangents at \(x=-2\) and \(x=2\). 2. The function decreases between those turning points, so \(f'(x)<0\) on \((-2,2)\). 3. The graph is concave up for \(x>0\), so in the displayed domain \(f''(x)>0\) on \((0,5)\). 4. At \(x=-2\), the graph changes from increasing to decreasing, so \(f\) has a local maximum. At \(x=2\), it changes from decreasing to increasing, so \(f\) has a local minimum. 5. The concavity changes at \(x=0\), so \(f\) has an inflection point there.

Answer

a) \(x=-2\) and \(x=2\) b) \((-2,2)\) c) \((0,5)\) d) Local maximum at \(x=-2\); local minimum at \(x=2\) e) Inflection point at \(x=0\)
53501212
One of the four graphs could represent a function \(f\) whose derivative is \(f'(x)=\cos(x)\) on \([0,2\pi]\). Identify the correct graph and justify your choice using zeros and signs of \(f'\).
Figure for problem 535012

Hints

- Mark where the given derivative is positive, zero, and negative. - Translate those signs into increasing and decreasing behavior of the original function. - Use the derivative's zeros to locate the original function's horizontal tangents.

Solution

1. The derivative is positive on \((0,\frac{\pi}{2})\), zero at \(x=\frac{\pi}{2}\), negative on \((\frac{\pi}{2},\frac{3\pi}{2})\), zero at \(x=\frac{3\pi}{2}\), and positive on \((\frac{3\pi}{2},2\pi)\). 2. Therefore, \(f\) must increase, then have a local maximum at \(x=\frac{\pi}{2}\), decrease to a local minimum at \(x=\frac{3\pi}{2}\), and then increase again. 3. Graph a has exactly this behavior. Thus graph a could represent \(f\).

Answer

Graph a
53501312
One of the four graphs could represent a function \(f\) whose derivative is \(f'(x)=\frac12x-1\). Identify the correct graph and justify your choice using the zero and sign of \(f'\).
Figure for problem 535013

Hints

- Find where the given derivative is zero. - Use the sign of the derivative on each side of that zero. - Use whether the derivative itself is increasing or decreasing to determine concavity.

Solution

1. The derivative has a zero at \(x=2\). 2. For \(x<2\), \(f'(x)<0\), so \(f\) decreases. For \(x>2\), \(f'(x)>0\), so \(f\) increases. Therefore, \(f\) has a local minimum at \(x=2\). 3. Since \(f'\) is linear with positive slope, \(f\) must be concave up. Only graph a is concave up and has its minimum at \(x=2\).

Answer

Graph a
55033912
The graph of \(q'\) is shown. A student makes two claims: 1. “\(q\) has a local minimum at \(x=-2\) because \(q'(-2)=0\).” 2. “\(q\) is concave up wherever \(q'>0\).” For each claim, decide whether it is correct. If it is incorrect, replace it with a correct conclusion supported by the graph.
Figure for problem 550339

Hints

- A zero of the derivative must be interpreted using the derivative's signs on both sides. - Keep the derivative's sign separate from whether the derivative itself is rising or falling. - Use one feature of the graph for extrema and a different feature for concavity.

Solution

1. Claim 1 is incorrect. At \(x=-2\), \(q'\) changes from positive to negative, so \(q\) has a local maximum, not a local minimum. 2. Claim 2 is incorrect. Concavity is determined by whether \(q'\) is increasing or decreasing, not by the sign of \(q'\). The derivative decreases on \((-5,0)\), so \(q\) is concave down there; it increases on \((0,5)\), so \(q\) is concave up there. Thus \(x=0\) is the x-coordinate of an inflection point.

Answer

1. Incorrect: \(q\) has a local maximum at \(x=-2\). 2. Incorrect: \(q\) is concave down on \((-5,0)\) and concave up on \((0,5)\); \(x=0\) is an inflection-point x-coordinate.
55616512
Instead of a freehand sketch, give an exact **graph blueprint**. For a differentiable function \(f\): - \(f'(x)>0\) for \(x<-2\), \(f'(x)<0\) for \(-2<x<1\), and \(f'(x)>0\) for \(x>1\); - \(f''(x)<0\) for \(x<0\) and \(f''(x)>0\) for \(x>0\); - \(f(-2)=4\), \(f(0)=1\), and \(f(1)=0\). Write the graph blueprint from left to right, splitting whenever monotonicity or concavity changes. Name every local extremum and inflection point with coordinates.

Hints

- Combine the sign of \(f'\) and the sign of \(f''\) on each interval. - Split the blueprint at \(-2\), \(0\), and \(1\). - Use the supplied function values only to place the named landmarks.

Solution

1. On \(( -\infty,-2)\), \(f'>0\) and \(f''<0\): increasing, concave down. 2. At \(x=-2\), \(f'\) changes positive to negative, so \((-2,4)\) is a local maximum. 3. On \((-2,0)\), \(f'<0\) and \(f''<0\): decreasing, concave down. 4. At \(x=0\), concavity changes from down to up, so \((0,1)\) is an inflection point. 5. On \((0,1)\), \(f'<0\) and \(f''>0\): decreasing, concave up. 6. At \(x=1\), \(f'\) changes negative to positive, so \((1,0)\) is a local minimum. 7. On \((1,\infty)\), \(f'>0\) and \(f''>0\): increasing, concave up.

Answer

Increasing/concave down on \(( -\infty,-2)\); local max \((-2,4)\); decreasing/concave down on \((-2,0)\); inflection \((0,1)\); decreasing/concave up on \((0,1)\); local min \((1,0)\); increasing/concave up on \((1,\infty)\).
52262512
For each function, build a text-only graph blueprint using algebra and derivatives. Report symmetry, all distinct real zeros, maximal intervals of increase and decrease, every local extremum with coordinates, and every stationary inflection point. Then match each function with every listed property that applies. Functions: (1) \(f(x)=2x^2-x^4\) (2) \(g(x)=x^3-3x\) (3) \(h(x)=x^3-3x^2+3x-1\) Properties: A: The graph is symmetric about the y-axis. B: The graph is symmetric about the origin. C: The function has exactly two local extrema. D: The graph has exactly one stationary inflection point. E: The function has exactly three distinct real zeros.

Hints

- Treat each formula as a separate graph-analysis problem before matching any properties. - Use the sign of the first derivative for monotonicity and local extrema. - A stationary inflection point needs both a horizontal tangent and a concavity change. - Use algebraic symmetry and factoring only for the symmetry and zero parts of the blueprint.

Solution

1. For \(f(x)=2x^2-x^4\), the graph is y-axis symmetric and the zeros are \(-\sqrt2,0,\sqrt2\). Since \(f'(x)=4x(1-x^2)\), \(f\) increases on \(( -\infty,-1)\) and \((0,1)\), and decreases on \((-1,0)\) and \((1,\infty)\). Thus the local maxima are \((-1,1)\) and \((1,1)\), and the local minimum is \((0,0)\). Its inflection points are not stationary. Therefore A and E apply. 2. For \(g(x)=x^3-3x\), the graph is origin-symmetric and the zeros are \(-\sqrt3,0,\sqrt3\). Since \(g'(x)=3(x^2-1)\), \(g\) increases on \(( -\infty,-1)\) and \((1,\infty)\), and decreases on \((-1,1)\). Thus \((-1,2)\) is a local maximum and \((1,-2)\) is a local minimum. Its inflection point at \(x=0\) is not stationary. Therefore B, C, and E apply. 3. Since \(h(x)=(x-1)^3\), its only zero is \(x=1\). The derivative \(h'(x)=3(x-1)^2\) is nonnegative and does not change sign, so \(h\) is strictly increasing on \(\mathbb{R}\) and has no local extremum. Because \(h''(x)=6(x-1)\) changes sign at \(x=1\) and \(h'(1)=0\), \((1,0)\) is a stationary inflection point. Therefore D applies.

Answer

(1) Blueprint: y-axis symmetry; zeros \(-\sqrt2,0,\sqrt2\); increasing on \(( -\infty,-1)\), \((0,1)\); decreasing on \((-1,0)\), \((1,\infty)\); local maxima \((-1,1)\), \((1,1)\); local minimum \((0,0)\); no stationary inflection point. Properties A, E. (2) Blueprint: origin symmetry; zeros \(-\sqrt3,0,\sqrt3\); increasing on \(( -\infty,-1)\), \((1,\infty)\); decreasing on \((-1,1)\); local maximum \((-1,2)\); local minimum \((1,-2)\); no stationary inflection point. Properties B, C, E. (3) Blueprint: zero \(1\); strictly increasing on \(\mathbb{R}\); no local extrema; stationary inflection point \((1,0)\). Property D.
52262612
For each function, build a text-only graph blueprint using algebra and derivatives. Report real zeros, maximal intervals of increase and decrease, all local extrema, every stationary inflection point, and any stated line symmetry. Then match each function with every statement that applies. Functions: (1) \(f(x)=x^4+1\) (2) \(g(x)=x^3+3x^2+3x+1\) (3) \(h(x)=x^2-2x+5\) Statements: A: The first derivative has exactly one real zero. B: The graph has a stationary inflection point. C: The function has no local extremum. D: The graph is symmetric about the line \(x=1\).

Hints

- Factor or complete the square before differentiating when that reveals a useful graph feature. - A zero of the first derivative does not automatically create a local extremum; check the sign on both sides. - For a stationary inflection point, verify a concavity change at a horizontal tangent. - Assemble all of the features for one function before matching its statements.

Solution

1. For \(f(x)=x^4+1\), \(f'(x)=4x^3\) has the single zero \(x=0\). The function decreases on \(( -\infty,0)\), increases on \((0,\infty)\), and has a local minimum at \((0,1)\). It has no real zeros and no stationary inflection point. Thus only A applies. 2. Since \(g(x)=(x+1)^3\), \(g'(x)=3(x+1)^2\) has the single zero \(x=-1\) but does not change sign. The function is strictly increasing on \(\mathbb{R}\), has no local extremum, and \(g''(x)=6(x+1)\) changes sign at \(-1\). Thus \((-1,0)\) is a stationary inflection point. A, B, and C apply. 3. For \(h(x)=(x-1)^2+4\), \(h'(x)=2(x-1)\) has the single zero \(x=1\). The function decreases on \(( -\infty,1)\), increases on \((1,\infty)\), and has a local minimum at \((1,4)\). It has no real zeros and is symmetric about \(x=1\). Thus A and D apply.

Answer

(1) Blueprint: no real zeros; decreasing then increasing at local minimum \((0,1)\); no stationary inflection point. Statement A. (2) Blueprint: zero and stationary inflection point \((-1,0)\); strictly increasing on \(\mathbb{R}\); no local extremum. Statements A, B, C. (3) Blueprint: no real zeros; decreasing on \(( -\infty,1)\), increasing on \((1,\infty)\); local minimum \((1,4)\); symmetry line \(x=1\). Statements A, D.
52632312
Let \(f(x)=x^4-4x^2\). Analyze the function and describe its graph. 1. Determine whether the graph is symmetric about the y-axis or the origin. 2. Find all zeros. 3. Find and classify all local extrema. 4. Describe the end behavior as \(x\to\pm\infty\).

Hints

- Even powers suggest y-axis symmetry. - Factor out the greatest common factor to find the zeros. - Use the first and second derivatives to find and classify extrema. - The leading term determines the graph's end behavior.

Solution

1. Because \(f(-x)=f(x)\), the graph is symmetric about the y-axis. 2. Factoring gives \(f(x)=x^2(x-2)(x+2)\). The zeros are \(x=0\), with multiplicity \(2\), and \(x=\pm2\), each with multiplicity \(1\). 3. The derivative is \(f'(x)=4x(x^2-2)\), so the critical numbers are \(x=0\) and \(x=\pm\sqrt{2}\). The second derivative is \(f''(x)=12x^2-8\). Thus, \((0, 0)\) is a local maximum, and \((\pm\sqrt{2}, -4)\) are local minima. 4. The leading term is \(x^4\), so \(f(x)\to\infty\) as \(x\to\pm\infty\). The graph passes through the intercepts and extrema, is symmetric about the y-axis, and has both ends rising.

Answer

1. The graph is symmetric about the y-axis. 2. The zeros are \(x=0\), with multiplicity \(2\), and \(x=\pm2\), each with multiplicity \(1\). 3. Local maximum: \((0, 0)\); local minima: \((-\sqrt{2}, -4)\) and \((\sqrt{2}, -4)\) 4. \(f(x)\to\infty\) as \(x\to\pm\infty\).
52632412
Let \(f(x)=-\frac{1}{2}x^4+4x^2-6\). 1. Find the x-intercepts using a substitution. 2. Find and classify all local extrema. 3. Describe the graph using its symmetry, key points, and end behavior.

Hints

- Substitute \(u=x^2\) to turn the quartic equation into a quadratic. - Remember both square roots when substituting back. - Use the first and second derivatives to find the extrema. - Use symmetry and end behavior to complete the graph description.

Solution

1. Set \(f(x)=0\) and multiply by \(-2\): \(x^4-8x^2+12=0\). Let \(u=x^2\). Then \(u^2-8u+12=(u-2)(u-6)=0\), so \(u=2\) or \(u=6\). Therefore, the x-intercepts occur at \(x=\pm\sqrt{2}\) and \(x=\pm\sqrt{6}\). 2. The derivative is \(f'(x)=-2x(x^2-4)\), so the critical numbers are \(x=-2\), \(x=0\), and \(x=2\). Since \(f''(x)=-6x^2+8\), \((0, -6)\) is a local minimum and \((\pm2, 2)\) are local maxima. 3. The graph is symmetric about the y-axis. It passes through the four x-intercepts, the local minimum, and the two local maxima. Since the leading coefficient is negative, both ends fall toward \(-\infty\).

Answer

1. The x-intercepts occur at \(x=\pm\sqrt{2}\) and \(x=\pm\sqrt{6}\). 2. Local minimum: \((0, -6)\); local maxima: \((-2, 2)\) and \((2, 2)\) 3. The graph is symmetric about the y-axis, passes through the listed intercepts and extrema, and satisfies \(f(x)\to-\infty\) as \(x\to\pm\infty\).
52992712
Let \(f(x)=4^x-2^x\). a) Find all zeros of \(f\). b) Find and classify the local extremum. c) Find every inflection point and state the concavity intervals. d) Describe the end behavior as \(x\to\infty\) and \(x\to-\infty\). e) Combine parts a)-d) into a left-to-right graph blueprint: state the monotonicity intervals and list the zero, extremum, and inflection point in their graph order.

Hints

- Rewrite everything in powers of \(2^x\) before solving the zero and critical-number equations. - The signs of the first and second derivatives determine the monotonicity and concavity pieces of the blueprint. - Use the limiting behavior to decide how the far-left and far-right pieces of the graph must continue. - Order the significant x-values only after computing each feature.

Solution

1. Rewrite \(4^x=(2^x)^2\). Then \(f(x)=2^x(2^x-1)\), so the only zero is \(x=0\). 2. \(f'(x)=\ln(2)2^x(2\cdot2^x-1)\). Thus the only critical number is \(x=-1\); \(f'\) is negative before \(-1\) and positive after it, so the point \((-1,-\tfrac14)\) is a local minimum. 3. \(f''(x)=(\ln2)^2 2^x(4\cdot2^x-1)\). It changes sign at \(x=-2\), giving the inflection point \((-2,-\tfrac{3}{16})\). The graph is concave down on \(( -\infty,-2)\) and concave up on \((-2,\infty)\). 4. As \(x\to\infty\), \(f(x)\to\infty\). As \(x\to-\infty\), \(f(x)\to0\) from below. 5. Therefore the blueprint is: approach \(y=0\) from below, concave down and decreasing; pass through the inflection point at \(x=-2\); continue decreasing concave up to the local minimum at \(x=-1\); then increase concave up through the zero at \(x=0\) and toward \(\infty\).

Answer

a) Zero: \((0,0)\). b) Local minimum: \((-1,-\tfrac14)\). c) Inflection point: \((-2,-\tfrac{3}{16})\); concave down on \(( -\infty,-2)\), concave up on \((-2,\infty)\). d) \(f(x)\to\infty\) as \(x\to\infty\); \(f(x)\to0^-\) as \(x\to-\infty\). e) Decreasing on \(( -\infty,-1)\), increasing on \((-1,\infty)\); left-to-right landmarks: inflection at \(x=-2\), minimum at \(x=-1\), zero at \(x=0\).
52992812
Let \(g(x)=2^x+4\cdot2^{-x}\). a) Explain without calculation why \(g\) has no zeros. b) Find the exact coordinates of the local extremum and classify it. c) Determine the concavity of \(g\) on \(\mathbb{R}\). d) Describe the end behavior as \(x\to\infty\) and \(x\to-\infty\). e) Combine the results into a left-to-right graph blueprint, including monotonicity, the extremum, concavity, and end behavior.

Hints

- Positivity of both exponential terms settles the zero question immediately. - Compare the two positive exponential terms in the first derivative to locate the turning point. - The sign of the second derivative tells whether the graph ever changes concavity. - A graph blueprint should connect the two ends through the extremum using the derivative information.

Solution

1. Both terms are positive for every real \(x\), so \(g(x)>0\) and there are no zeros. 2. \(g'(x)=\ln(2)(2^x-4\cdot2^{-x})\). Solving \(g'(x)=0\) gives \(x=1\). The derivative is negative for \(x<1\) and positive for \(x>1\), so \((1,4)\) is a local minimum. 3. \(g''(x)=(\ln2)^2(2^x+4\cdot2^{-x})>0\) for every real \(x\), so the graph is concave up everywhere. 4. As \(x\to\infty\), the term \(2^x\) makes \(g(x)\to\infty\). As \(x\to-\infty\), the term \(4\cdot2^{-x}\) makes \(g(x)\to\infty\). 5. Thus the graph descends from \(\infty\), remains concave up, reaches its minimum at \((1,4)\), and then rises to \(\infty\), staying above the x-axis throughout.

Answer

a) No zeros because \(g(x)>0\) for all \(x\). b) Local minimum: \((1,4)\). c) Concave up on \(\mathbb{R}\). d) \(g(x)\to\infty\) as \(x\to\pm\infty\). e) Decreasing and concave up on \(( -\infty,1)\); minimum \((1,4)\); increasing and concave up on \((1,\infty)\).
53237212
The graph shown is the graph of the first derivative \(f'\) of a function \(f\). Determine whether each statement is true or false. Justify your answer. a) The function \(f\) is strictly increasing on \(-1<x<1\). b) The function \(f\) has a local maximum at \(x=3\). c) The graph of \(f\) is concave down on \(0<x<2\).
Figure for problem 532372

Hints

- What does the sign of \(f'\) tell you about whether \(f\) is increasing or decreasing? - What sign change of \(f'\) indicates a local maximum or minimum of \(f\)? - How does the slope of the graph of \(f'\) relate to \(f''\)?

Solution

1. Statement a is true. On \(-1<x<1\), the graph of \(f'\) is above the x-axis, so \(f'(x)>0\). Therefore, \(f\) is strictly increasing there. 2. Statement b is false. At \(x=3\), \(f'\) changes from negative to positive. Therefore, \(f\) has a local minimum, not a local maximum. 3. Statement c is true. On \(0<x<2\), the graph of \(f'\) is decreasing. Therefore, \(f''(x)<0\), so \(f\) is concave down there.

Answer

a) True; \(f'(x)>0\) on \(-1<x<1\). b) False; \(f'\) changes from negative to positive at \(x=3\), so \(f\) has a local minimum. c) True; \(f'\) is decreasing on \(0<x<2\), so \(f''(x)<0\).
53238012
Let \(f(x)=\frac{1}{2}x^4-4x^2+6\). The graph shown is a different polynomial function \(g\). a) Use two different properties to explain why the graph cannot represent \(f\). b) Analyze \(f\): 1. Determine its end behavior. 2. Find all zeros exactly and approximately to the nearest hundredth. 3. Find and classify all local extrema.
Figure for problem 532380

Hints

- Compare symmetry, intercepts, end behavior, or extrema for part a. - Use the leading term to determine the end behavior. - Substitute \(u=x^2\) to solve the quartic equation. - Use the first and second derivatives to find and classify extrema.

Solution

1. The graph shown cannot represent \(f\). For example, \(f\) is even and therefore symmetric about the y-axis, while the displayed graph is symmetric about \(x=1\). Also, \(f(0)=6\), but the displayed graph has y-intercept \((0, 1)\). 2. The positive leading coefficient and even degree give \(f(x)\to\infty\) as \(x\to\pm\infty\). 3. Solving \(\frac{1}{2}x^4-4x^2+6=0\) and substituting \(u=x^2\) gives \(u^2-8u+12=0\). Thus, \(u=2\) or \(u=6\), so the zeros are \(x=\pm\sqrt{2}\approx\pm1.41\) and \(x=\pm\sqrt{6}\approx\pm2.45\). 4. The derivative is \(f'(x)=2x(x^2-4)\), so the critical numbers are \(x=-2, 0, 2\). Since \(f''(x)=6x^2-8\), \((0, 6)\) is a local maximum and \((-2, -2)\) and \((2, -2)\) are local minima.

Answer

a) Possible reasons include: \(f\) is symmetric about the y-axis, but the displayed graph is symmetric about \(x=1\); and \(f(0)=6\), but the displayed graph has y-intercept \((0, 1)\). b) 1. \(f(x)\to\infty\) as \(x\to\pm\infty\) 2. \(x=\pm\sqrt{2}\approx\pm1.41\) and \(x=\pm\sqrt{6}\approx\pm2.45\) 3. Local maximum: \((0, 6)\); local minima: \((-2, -2)\) and \((2, -2)\)
53241712
The graph of \(f'\) is shown. a) Find the x-coordinates of all local extrema of \(f\). Classify each and justify your answer. b) Find the x-coordinate of the inflection point of \(f\) and justify your answer from the derivative graph.
Figure for problem 532417

Hints

- Use zeros and sign changes of the derivative for local extrema. - For concavity, track whether the derivative graph is increasing or decreasing. - A turning point of \(f'\) corresponds to a concavity change of \(f\) when that direction changes.

Solution

1. Local extrema of \(f\) occur at zeros of \(f'\) where the sign changes. 2. At \(x=-1\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. 3. At \(x=3\), \(f'\) changes from negative to positive, so \(f\) has a local minimum. 4. The derivative graph has a local minimum at \(x=1\), changing from decreasing to increasing. Thus \(f\) changes from concave down to concave up there, so \(x=1\) is an inflection point.

Answer

a) Local maximum at \(x=-1\); local minimum at \(x=3\). b) Inflection point at \(x=1\).
53243612
The figure shows two graphs labeled \(g_1\) and \(g_2\). One graph represents a function \(f\), and the other represents its derivative \(f'\). a) Decide which graph represents \(f\) and which represents \(f'\). Justify your answer using critical numbers or increasing and decreasing behavior. b) Estimate the coordinates of the local maximum, local minimum, and inflection point of \(f\). c) Find the interval on which \(f\) is strictly decreasing.
Figure for problem 532436

Hints

- Compare the zeros of one graph with the horizontal tangents of the other. - A function decreases where its derivative is negative. - An inflection point of \(f\) corresponds to a local extremum of \(f'\). - Read the requested coordinates from the graph of \(f\).

Solution

1. The graph labeled \(g_1\) has horizontal tangents at \(x=-2\) and \(x=2\), while the graph labeled \(g_2\) is zero at those values. Also, \(g_1\) decreases between \(-2\) and \(2\), where \(g_2\) is negative. Therefore, \(g_1\) represents \(f\) and \(g_2\) represents \(f'\). 2. Reading from \(g_1\), the local maximum is \((-2, 3)\), the local minimum is \((2, -1)\), and the inflection point is \((0, 1)\). 3. Since \(g_2\) is negative for \(-2<x<2\), \(f\) is strictly decreasing on \([-2, 2]\).

Answer

a) \(g_1\) represents \(f\), and \(g_2\) represents \(f'\). b) Local maximum: \((-2, 3)\); local minimum: \((2, -1)\); inflection point: \((0, 1)\) c) \([-2, 2]\)
53244012
The graph shows the derivative \(f'\) of a function \(f\) on \([-4, 4]\). a) On which intervals is \(f\) strictly increasing, and on which intervals is it strictly decreasing? b) At which \(x\)-values does \(f\) have local extrema? Classify each as a local maximum or local minimum. c) Explain why \(f\) has an inflection point at \(x = 0\).
Figure for problem 532440

Hints

- Use the sign of \(f'\) to determine where \(f\) increases or decreases. - Check the direction of each sign change at a zero of \(f'\). - A local extremum of \(f'\) indicates a possible inflection point of \(f\).

Solution

1. The derivative is positive on \((-4, -2)\) and \((2, 4)\), so \(f\) is strictly increasing on \([-4, -2]\) and \([2, 4]\). The derivative is negative on \((-2, 2)\), so \(f\) is strictly decreasing on \([-2, 2]\). 2. At \(x = -2\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. At \(x = 2\), \(f'\) changes from negative to positive, so \(f\) has a local minimum. 3. The graph of \(f'\) has a local minimum at \(x = 0\), so \(f''\) changes sign there. Therefore, the concavity of \(f\) changes at \(x = 0\), giving an inflection point.

Answer

a) Increasing on \([-4, -2]\) and \([2, 4]\); decreasing on \([-2, 2]\) b) Local maximum at \(x = -2\); local minimum at \(x = 2\) c) \(f'\) has a local minimum at \(x = 0\), so \(f\) changes concavity there.
53244112
The graph shows the first derivative \(f'\) of a polynomial function \(f\) on \([-5, 5]\). a) Find the intervals on which \(f\) is strictly increasing and strictly decreasing. b) Find the \(x\)-coordinates of all local maxima and local minima of \(f\). Briefly justify your answer using the graph of \(f'\). c) Estimate the \(x\)-coordinates of all inflection points of \(f\) to the nearest tenth. Then describe where \(f\) is concave up and concave down using those estimates.
Figure for problem 532441

Hints

- Use the sign of \(f'\) for increasing and decreasing intervals. - Use sign changes of \(f'\) to classify local extrema. - Inflection points of \(f\) occur where \(f'\) changes from increasing to decreasing or vice versa. - The graph of \(f\) is concave up where \(f'\) is increasing and concave down where \(f'\) is decreasing.

Solution

1. The derivative is positive on \((-5, -4)\) and \((-1, 4)\), so \(f\) is strictly increasing on \([-5, -4]\) and \([-1, 4]\). It is negative on \((-4, -1)\) and \((4, 5)\), so \(f\) is strictly decreasing on \([-4, -1]\) and \([4, 5]\). 2. At \(x = -4\), \(f'\) changes from positive to negative, giving a local maximum. At \(x = -1\), it changes from negative to positive, giving a local minimum. At \(x = 4\), it changes from positive to negative, giving another local maximum. 3. Inflection points of \(f\) occur where \(f'\) has local extrema. From the graph, these occur at about \(x \approx -2.7\) and \(x = 2\). Using these estimates, \(f'\) increases approximately on \((-2.7, 2)\), so \(f\) is concave up there. It decreases approximately on \((-5, -2.7)\) and \((2, 5)\), so \(f\) is concave down there.

Answer

a) Increasing on \([-5, -4]\) and \([-1, 4]\); decreasing on \([-4, -1]\) and \([4, 5]\) b) Local maxima at \(x = -4\) and \(x = 4\); local minimum at \(x = -1\) c) Inflection points at approximately \(x \approx -2.7\) and \(x = 2\); concave up approximately on \((-2.7, 2)\); concave down approximately on \((-5, -2.7)\) and \((2, 5)\)
53252312
Panels A, B, and C show three function graphs. Panels (1), (2), and (3) show their derivative graphs in a different order. Match each function graph, A, B, and C, with the correct derivative graph, (1), (2), or (3). Justify your matches using zeros, local maxima and minima, and increasing and decreasing behavior.
Figure for problem 532523

Hints

- Match horizontal tangents of each function with zeros of its derivative. - A derivative is positive where its function increases and negative where its function decreases. - Pay attention to the number and locations of local extrema.

Solution

1. Graph A is an upward-opening parabola with a minimum at \(x = 1\). It decreases for \(x < 1\) and increases for \(x > 1\), so its derivative must be an increasing line that is zero at \(x = 1\). Therefore, A matches (2). 2. Graph B has a local maximum at \(x = -2\) and a local minimum at \(x = 2\). Its derivative must be zero at \(x = -2\) and \(x = 2\), negative between those values, and positive outside them. Therefore, B matches (3). 3. Graph C has a maximum at \(x = 0\), increases for \(x < 0\), and decreases for \(x > 0\). Its derivative must be positive to the left of \(0\), zero at \(0\), and negative to the right. Therefore, C matches (1).

Answer

A \(\rightarrow\) (2); B \(\rightarrow\) (3); C \(\rightarrow\) (1)
53254212
The graph of the derivative \(f'\) of a function \(f\) is shown. Determine whether each statement is true or false, and justify your answer. a) The graph of \(f\) has a local minimum at \(x=0\). b) The function \(f\) is strictly decreasing on \([0, 4]\). c) If \(f(0)=2\), then \(f(3)>2\). d) The graph of \(f\) has an inflection point at \(x=2\).
Figure for problem 532542

Hints

- Use the sign of \(f'\) to determine whether \(f\) increases or decreases. - What does a sign-changing zero of the derivative indicate? - Compare function values using monotonicity. - How are extrema of \(f'\) related to inflection points of \(f\)?

Solution

1. At \(x=0\), \(f'\) changes from negative to positive, so \(f\) has a local minimum. Statement a is true. 2. On \((0, 4)\), \(f'(x)>0\), so \(f\) is strictly increasing, not decreasing. Statement b is false. 3. Since \(f'(x)>0\) on \((0, 3]\), \(f(3)>f(0)=2\). Statement c is true. 4. An extremum of \(f'\) corresponds to an inflection point of \(f\). Since \(f'\) has a local maximum at \(x=2\), statement d is true.

Answer

a) True b) False c) True d) True
53255512
The graph of a function \(f\) has seven marked x-values, \(x_1\) through \(x_7\). Use the graph to answer each question. a) At which marked value is \(f(x)\) smallest? b) Among the five interior values \(x_2, x_3, x_4, x_5, x_6\), where is the tangent slope \(f'(x)\) greatest? c) At which marked value is \(f''(x)<0\)? d) Which marked values correspond to inflection points of \(f\)?
Figure for problem 532555

Hints

- First relate \(f(x)\), \(f'(x)\), and \(f''(x)\) to the graph. - The function value is the point’s vertical coordinate. - The first derivative gives the tangent slope. - A negative second derivative corresponds to concave-down behavior. - An inflection point occurs where the graph changes concavity.

Solution

1. Compare the y-coordinates of all seven marked points. The lowest marked point is at \(x_6\), where \(f(x_6)\approx-1.54\). 2. The first derivative is the tangent slope. The graph is nearly horizontal at \(x_2\), \(x_4\), and \(x_6\), decreasing at \(x_5\), and increasing steeply at \(x_3\). Therefore, the greatest slope among the five interior values occurs at \(x_3\). 3. A negative second derivative means the graph is concave down. The graph is concave down between its inflection-point x-coordinates \(x=-1\) and \(x=2\). Of the marked values, only \(x_4\) lies strictly between them. 4. The graph changes concavity at \(x_3=-1\) and \(x_5=2\). Therefore, the inflection points correspond to \(x_3\) and \(x_5\).

Answer

a) \(x_6\) b) \(x_3\) c) \(x_4\) d) \(x_3\) and \(x_5\)
53255812
The graph shown is the first derivative \(f'\) of a polynomial function \(f\). Determine whether each statement is true or false. a) The graph of \(f\) is concave down on \([0, 2]\). b) The graph of \(f\) has an inflection point at \(x=1\). c) On the displayed interval \(-3\le x\le5\), the graph of \(f\) has exactly two inflection points. d) The function \(f\) is strictly decreasing on \([1, 4]\). e) The graph of \(f\) has a local maximum at \(x=-2\).
Figure for problem 532558

Hints

- Review how monotonicity, concavity, extrema, and inflection points of \(f\) appear in the graph of \(f'\). - Connect the sign of \(f'\) to whether \(f\) is increasing or decreasing. - Connect the monotonicity of \(f'\) to the concavity of \(f\). - What sign changes of \(f'\) produce local extrema of \(f\)? - Where does \(f\) have inflection points when the graph of \(f'\) is given?

Solution

1. Statement a is true. The graph of \(f'\) is decreasing on \([0, 2]\), so \(f''(x)<0\) there and \(f\) is concave down. 2. Statement b is false. At \(x=1\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. The graph of \(f'\) does not have a local extremum there, so \(f\) does not have an inflection point there. 3. Statement c is true. The graph of \(f'\) has local extrema at \(x=1-\sqrt{3}\approx-0.73\) and \(x=1+\sqrt{3}\approx2.73\). Therefore, \(f\) has exactly two inflection points on the displayed interval. 4. Statement d is true. On \((1, 4)\), \(f'(x)<0\), with zeros only at the endpoints. Therefore, \(f\) is strictly decreasing on \([1, 4]\). 5. Statement e is false. At \(x=-2\), \(f'\) changes from negative to positive, so \(f\) has a local minimum.

Answer

a) True b) False c) True d) True e) False
53256412
The function \(f\) is defined by \(f(x)=\frac{1}{3}x^3-x^2-3x+2\). The displayed graph represents a function \(g\). Give three different mathematical reasons—such as end behavior, sign, or behavior at critical numbers—showing that the displayed graph cannot represent the derivative \(f'\).
Figure for problem 532564

Hints

- First compute \(f'(x)\). - Compare the degree and leading coefficient with the displayed graph. - Compare signs on intervals where \(f\) increases or decreases. - Compare the directions of sign changes at the zeros.

Solution

1. Differentiate: \(f'(x)=x^2-2x-3\). 2. End behavior: \(f'\) is an upward-opening parabola, so \(f'(x)\to\infty\) as \(x\to\pm\infty\). The displayed graph opens downward. 3. Sign and monotonicity: \(f'(x)<0\) on \((-1,3)\), so \(f\) decreases there. The displayed graph is positive on that interval. 4. Critical-number behavior: At \(x=-1\), the true derivative changes from positive to negative, which gives \(f\) a local maximum. The displayed graph changes from negative to positive there, which would indicate a local minimum.

Answer

Three valid reasons are: 1. The true derivative \(f'(x)=x^2-2x-3\) opens upward, but the displayed graph opens downward. 2. The true derivative is negative on \((-1,3)\), but the displayed graph is positive there. 3. At \(x=-1\), the true derivative changes from positive to negative, while the displayed graph changes from negative to positive.
53256712
Let \(f(x)=x^3-3x^2\). Graph A and Graph B are shown. For each graph, give at least two different mathematical reasons why it cannot represent \(f\).
Figure for problem 532567

Hints

- Compare the end behavior of a positive-leading-coefficient cubic with each graph. - Factor \(f\) to identify its zeros and their multiplicities. - Check whether \(f\) is even or odd. - Find the critical numbers and compare the locations and classifications of the extrema.

Solution

1. Graph A cannot represent \(f\). The function has end behavior \(f(x)\to\infty\) as \(x\to\infty\) and \(f(x)\to-\infty\) as \(x\to-\infty\), while Graph A has the opposite end behavior. Also, \(f(x)=x^2(x-3)<0\) for every \(x<0\), but Graph A lies above the x-axis there. In addition, \(f\) has a local maximum at \((0, 0)\) and a local minimum at \((2, -4)\), while Graph A reverses those classifications. 2. Graph B cannot represent \(f\). Graph B is symmetric about the origin, but \(f\) is neither even nor odd. Graph B crosses the x-axis at the origin, while \(f(x)=x^2(x-3)\) has a double zero there and only touches the axis. Also, the local maximum of \(f\) is at the origin, not at a negative x-value as shown in Graph B.

Answer

Graph A: It has the wrong end behavior; it lies above the x-axis for negative \(x\), although \(f(x)<0\) there; and it reverses the local maximum and local minimum. Graph B: It has origin symmetry, but \(f\) has no such symmetry; it crosses rather than touches the x-axis at \(x=0\); and its local maximum is at the wrong x-value.
53259012
The graph shown is the derivative \(f'\) of a function \(f\). a) Find and classify the critical numbers of \(f\). b) Determine the intervals where \(f\) is concave up and concave down. c) Find the x-coordinates of all inflection points of \(f\). d) Explain why \(f(-2)>f(-4)\).
Figure for problem 532590

Hints

- Use zeros and sign changes of \(f'\) to classify critical numbers of \(f\). - At a zero of \(f'\), check whether the derivative changes sign or only touches the x-axis. - How does the monotonicity of \(f'\) determine the concavity of \(f\)? - Inflection-point x-coordinates of \(f\) correspond to local extrema of \(f'\). - Use the sign of \(f'\) to compare \(f(-2)\) and \(f(-4)\).

Solution

1. At \(x=-4\), \(f'\) changes from negative to positive, so \(f\) has a local minimum. At \(x=-1\), \(f'\) has a double zero and does not change sign, so \(f\) has no local extremum there; instead, it has a stationary inflection point. 2. On the displayed interval, \(f'\) is increasing on \([-5, -3)\) and \((-1, 0.5]\), so \(f\) is concave up there. It is decreasing on \((-3, -1)\), so \(f\) is concave down there. 3. The graph of \(f'\) has local extrema at \(x=-3\) and \(x=-1\). Therefore, these are the x-coordinates of the inflection points of \(f\). 4. For \(-4<x\le-2\), \(f'(x)>0\), so \(f\) is strictly increasing on \([-4, -2]\). Therefore, \(f(-2)>f(-4)\).

Answer

a) Local minimum at \(x=-4\); stationary inflection point at \(x=-1\). b) Concave up on \([-5, -3)\) and \((-1, 0.5]\); concave down on \((-3, -1)\). c) \(x=-3\) and \(x=-1\) d) \(f(-2)>f(-4)\) because \(f\) is strictly increasing on \([-4, -2]\).
53259312
The graph of a cubic polynomial \(f\) is shown. a) Read the coordinates of the local maximum \(H\), local minimum \(T\), and inflection point \(W\). b) Use the points to find an equation for \(f\). Show your work. c) Find all zeros of \(f\), including multiplicities.
Figure for problem 532593

Hints

- Read the three marked points carefully. - At each marked local extremum, the first derivative is \(0\). - Use function-value and derivative conditions at extrema and inflection points. - The inflection point on the y-axis simplifies the cubic form. - A local extremum on the x-axis is a multiple zero.

Solution

1. From the graph, \(H=(-1, 4)\), \(T=(1, 0)\), and \(W=(0, 2)\). 2. Let \(f(x)=ax^3+bx^2+cx+d\). Since \(W=(0, 2)\) is an inflection point, \(f(0)=2\) and \(f''(0)=0\), so \(d=2\) and \(b=0\). 3. Using \(T=(1, 0)\), the equations \(f(1)=0\) and \(f'(1)=0\) give \(a+c=-2\) and \(3a+c=0\). Thus, \(a=1\) and \(c=-3\), so \(f(x)=x^3-3x+2\). 4. Factoring gives \(f(x)=(x-1)^2(x+2)\). Therefore, \(x=1\) is a double zero and \(x=-2\) is a simple zero.

Answer

a) \(H=(-1, 4)\), \(T=(1, 0)\), \(W=(0, 2)\) b) \(f(x)=x^3-3x+2\) c) \(x=1\), multiplicity \(2\); \(x=-2\), multiplicity \(1\)
53259412
A cubic polynomial \(f(x)=ax^3+bx^2+cx+d\) has a local maximum at \(H=(-1, 4)\) and a local minimum at \(T=(1, 0)\). a) A student claims that such a function can also pass through \(P=(2, 5)\). Find the function determined by the two extrema and show that the claim is false. b) Use the graph to find the actual value of \(f(2)\) and the inflection point \(W\). Explain why \(W\) is consistent with the graph’s point symmetry.
Figure for problem 532594

Hints

- A cubic has four coefficients, and the two extrema provide four equations. - At each extremum, use both the point and zero-slope conditions. - Substitute \(x=2\) to test the student's point. - Find the midpoint of the two extrema.

Solution

1. The extrema give \(f(-1)=4\), \(f(1)=0\), \(f'(-1)=0\), and \(f'(1)=0\). Solving these four equations gives \(a=1\), \(b=0\), \(c=-3\), and \(d=2\). Thus, \(f(x)=x^3-3x+2\). 2. Evaluating at \(x=2\) gives \(f(2)=8-6+2=4\ne5\), so \(P=(2, 5)\) is not on the graph. 3. The graph shows \(f(2)=4\) and \(W=(0, 2)\). The midpoint of \(H=(-1, 4)\) and \(T=(1, 0)\) is \((0, 2)\), so the extrema are paired by a half-turn about the inflection point.

Answer

a) \(f(x)=x^3-3x+2\), and \(f(2)=4\ne5\), so the claim is false. b) \(f(2)=4\) and \(W=(0, 2)\). The point \(W\) is the midpoint of \(H\) and \(T\), matching the graph's point symmetry.
53259812
The graph shows two functions labeled a and b. One graph represents a differentiable function \(f\), and the other represents its derivative \(f'\). Explain which graph is \(f\) and which is \(f'\).
Figure for problem 532598

Hints

- Compare turning points of one graph with zeros of the other. - Compare increasing and decreasing intervals with the sign of the candidate derivative graph. - Both relationships must agree for the match to be valid.

Solution

1. If one graph is \(f'\), its zeros must occur at horizontal tangents of \(f\). 2. Graph a has a local maximum at \(x=-2\) and a local minimum at \(x=2\). Graph b has zeros at exactly \(x=-2\) and \(x=2\). 3. Graph a decreases on \((-2,2)\), while graph b is negative there. Graph a increases for \(x<-2\) and \(x>2\), while graph b is positive there. 4. Therefore, graph a represents \(f\), and graph b represents \(f'\).

Answer

Graph a represents \(f\); graph b represents \(f'\).
53259912
Panel a) shows the derivative graphs \(f'\) and \(g'\). Panel b) shows four candidate graphs labeled a, b, c, and d for the original functions. Match \(f'\) and \(g'\) with the correct graphs of \(f\) and \(g\). Justify your choices using monotonicity and local extrema.
Figure for problem 532599

Hints

- The sign of a derivative determines whether its original function increases or decreases. - A sign-changing derivative zero corresponds to a local extremum. - Match each candidate using both the critical numbers and the monotonicity pattern.

Solution

1. The graph of \(f'\) has zeros at \(x=0\) and \(x=2\). It is positive for \(x<0\) and \(x>2\), and negative for \(0<x<2\). 2. Therefore, \(f\) must increase, then decrease, then increase, with a local maximum at \(x=0\) and a local minimum at \(x=2\). Candidate a has this behavior. 3. The graph of \(g'\) is positive for \(x<1\), zero at \(x=1\), and negative for \(x>1\). 4. Therefore, \(g\) must increase before \(x=1\), decrease afterward, and have a local maximum at \(x=1\). Candidate b has this behavior.

Answer

\(f'\) matches candidate a for \(f\); \(g'\) matches candidate b for \(g\).
53260012
Consider the family of functions \(f_a(x)=x^3-ax\), where \(a\ge0\). The figure shows three graphs from the family, labeled p, q, and r. a) Find the value of \(a\) for each graph. Justify your matches using the zeros. b) State the symmetry shared by all graphs and verify it algebraically. c) For \(a>0\), find the coordinates of the local maximum and local minimum in terms of \(a\). d) For which values of \(a\ge0\) does \(f_a\) have exactly three distinct real zeros? e) Using your derivative results, give a text-only graph blueprint for the two structurally different cases \(a=0\) and \(a>0\). For each case, state end behavior, monotonicity, local extrema, and the inflection-point x-coordinate in left-to-right order.
Figure for problem 532600

Hints

- Factor the function to find its zeros. - Compare \(f_a(-x)\) with \(f_a(x)\). - Use the first and second derivatives to locate and classify extrema. - Determine when \(\pm\sqrt{a}\) are distinct from zero. - For the final blueprint, distinguish the degenerate case \(a=0\) from \(a>0\); the derivative has a different zero structure in those two cases.

Solution

1. Factor \(f_a(x)=x(x^2-a)\). Graph p has only the zero \(x=0\), so \(a=0\). Graph q has zeros \(-1, 0, 1\), so \(a=1\). Graph r has zeros \(-2, 0, 2\), so \(a=4\). 2. Since \(f_a(-x)=-f_a(x)\), every graph is symmetric about the origin. 3. The first derivative is \(f_a'(x)=3x^2-a\), so the critical numbers are \(x=\pm\sqrt{\frac{a}{3}}\). The second derivative is \(f_a''(x)=6x\). 4. The local maximum is \(\left(-\sqrt{\frac{a}{3}}, \frac{2a}{3}\sqrt{\frac{a}{3}}\right)\), and the local minimum is \(\left(\sqrt{\frac{a}{3}}, -\frac{2a}{3}\sqrt{\frac{a}{3}}\right)\). 5. The zeros are \(0\) and \(\pm\sqrt{a}\). They are three distinct real numbers exactly when \(a>0\). 6. For \(a=0\), \(f_0(x)=x^3\): it is increasing on \(\mathbb{R}\), has no local extremum, has a stationary inflection point at \((0,0)\), and runs from \(-\infty\) to \(\infty\). 7. For \(a>0\), the graph increases on \(( -\infty,-\sqrt{a/3})\), decreases on \((-\sqrt{a/3},\sqrt{a/3})\), and increases on \((\sqrt{a/3},\infty)\). It has the local maximum and minimum from part c, a nonstationary inflection point at \((0,0)\), and the same cubic end behavior.

Answer

a) p: \(a=0\); q: \(a=1\); r: \(a=4\) b) Symmetric about the origin c) Local maximum: \(\left(-\sqrt{\frac{a}{3}}, \frac{2a}{3}\sqrt{\frac{a}{3}}\right)\); local minimum: \(\left(\sqrt{\frac{a}{3}}, -\frac{2a}{3}\sqrt{\frac{a}{3}}\right)\) d) \(a>0\) e) \(a=0\): increasing on \(\mathbb{R}\), no extrema, stationary inflection at \((0,0)\), cubic end behavior. For \(a>0\): increase → local maximum at \(x=-\sqrt{a/3}\) → decrease through the inflection at \(x=0\) → local minimum at \(x=\sqrt{a/3}\) → increase, with left end down and right end up.
53260212
The graph of \(f'\) is shown. Determine whether each statement about \(f\) is true or false. Justify your answers. (1) \(f\) is strictly increasing on \([-2,1]\). (2) \(f\) has a local minimum at \(x=1\). (3) The graph of \(f\) has an inflection point at approximately \(x=2.1\). (4) \(f(3)>f(1)\).
Figure for problem 532602

Hints

- Use the sign of \(f'\) for monotonicity and local extrema. - Use whether \(f'\) is increasing or decreasing for concavity. - The comparison \(f(3)\) versus \(f(1)\) follows from monotonicity on \((1,3)\); no accumulation concept is needed.

Solution

1. Statement (1) is true. The graph of \(f'\) is positive on \((-2,1)\), so \(f\) is strictly increasing there. 2. Statement (2) is false. At \(x=1\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. 3. Statement (3) is true. The graph of \(f'\) has a local minimum at approximately \(x=2.1\), changing from decreasing to increasing; therefore \(f\) changes from concave down to concave up there. 4. Statement (4) is false. Since \(f'(x)<0\) on \((1,3)\), \(f\) is strictly decreasing on that interval, so \(f(3)<f(1)\).

Answer

(1) True. (2) False. (3) True. (4) False.
53260612
Four graphs labeled a, b, c, and d are shown. Three represent a function \(f\), its first derivative \(f'\), and its second derivative \(f''\). Identify the three graphs and explain why the remaining graph cannot belong to the derivative chain.
Figure for problem 532606

Hints

- A derivative's zeros correspond to horizontal tangents of the function above it in the chain. - The sign of a derivative must agree with the increasing/decreasing behavior of its parent function. - Test the graphs pairwise until two consecutive derivative relationships both work.

Solution

1. Graph b has a local maximum at \(x=-1\) and a local minimum at \(x=1\). Graph a has zeros at those x-values and signs consistent with the increasing and decreasing intervals of graph b. Thus graph a is the derivative of graph b. 2. Graph c has extrema where graph b is zero, and its monotonicity agrees with the sign of graph b. Thus graph b is the derivative of graph c. 3. Therefore, graph c represents \(f\), graph b represents \(f'\), and graph a represents \(f''\). 4. Graph d has the opposite monotonicity relationship and cannot complete this derivative chain.

Answer

Graph c is \(f\); graph b is \(f'\); graph a is \(f''\); graph d does not belong.
53261512
The graph of \(f'\) is shown. a) Find the intervals on which \(f\) is strictly increasing and strictly decreasing. Classify every local extremum. b) A candidate function is \(f(x)=-\frac13x^3+4x-1\). Differentiate it to verify that its derivative matches the displayed graph. c) Does \(f\) have an inflection point at \(x=0\)? Justify your answer from the graph of \(f'\).
Figure for problem 532615

Hints

- Use the sign of the derivative graph for monotonicity and extrema. - Verify the candidate function by differentiating it. - For concavity, track whether the derivative graph is increasing or decreasing.

Solution

1. Since \(f'>0\) on \((-2,2)\), \(f\) is strictly increasing there. Since \(f'<0\) on \(( -\infty,-2)\) and \((2,\infty)\), \(f\) is strictly decreasing there. The sign changes give a local minimum at \(x=-2\) and a local maximum at \(x=2\). 2. Differentiating \(f(x)=-\frac13x^3+4x-1\) gives \(f'(x)=4-x^2\), matching the displayed graph. 3. Yes. The derivative graph has a local maximum at \(x=0\), changing from increasing to decreasing. Therefore \(f\) changes from concave up to concave down at \(x=0\).

Answer

a) Increasing on \((-2,2)\); decreasing on \(( -\infty,-2)\) and \((2,\infty)\). Local minimum at \(x=-2\); local maximum at \(x=2\). b) \(f'(x)=4-x^2\), matching the graph. c) Yes, \(x=0\) is an inflection point.
53262112
The graph shows a function \(g\) defined for all real numbers. A function \(f\) has derivative \(f'(x) = g(x) - 1\). a) Find the \(x\)-coordinates of all local extrema of \(f\). Classify each as a local maximum or local minimum, and justify your answer. b) Find the \(x\)-coordinate of the inflection point of \(f\). Justify your answer.
Figure for problem 532621

Hints

- Set \(f'(x) = 0\) by finding where \(g(x) = 1\). - Compare \(g(x)\) with \(1\) on each interval. - An inflection point of \(f\) occurs where \(f'\) has a local extremum.

Solution

1. Local extrema of \(f\) occur where \(f'(x) = 0\), so solve \(g(x) = 1\). From the graph, this occurs at \(x = -2\) and \(x = 2\). 2. For \(x < -2\), \(g(x) < 1\), so \(f'(x) < 0\). For \(-2 < x < 2\), \(g(x) > 1\), so \(f'(x) > 0\). Thus, \(f\) has a local minimum at \(x = -2\). 3. For \(-2 < x < 2\), \(f'(x) > 0\), and for \(x > 2\), \(f'(x) < 0\). Thus, \(f\) has a local maximum at \(x = 2\). 4. Since \(f''(x) = g'(x)\), an inflection point of \(f\) occurs where \(g\) has a local extremum. The graph of \(g\) has a maximum at \(x = 0\), so \(f\) has an inflection point there.

Answer

a) Local minimum at \(x = -2\); local maximum at \(x = 2\) b) Inflection point at \(x = 0\)
53263112
The graph shows the derivative \(f'\) of a differentiable function \(f\) defined for all real numbers. a) Find all local extrema of \(f\). Classify each as a local minimum or local maximum. b) At which \(x\)-value does the graph of \(f\) have its greatest slope? What is that slope? c) Find the \(x\)-values where the tangent to the graph of \(f\) is parallel to the line \(g(x) = 1.5x - 4\). d) The derivative has the form \(f'(x) = a(x-d)^2 + c\). Determine \(a\), \(d\), and \(c\) from the graph.
Figure for problem 532631

Hints

- Use zeros and sign changes of \(f'\) to classify local extrema. - The largest value of \(f'\) is the greatest slope of \(f\). - Parallel lines have equal slopes. - Read the vertex to identify \(d\) and \(c\), then use another point to find \(a\).

Solution

1. The derivative is zero at \(x = 0\) and \(x = 4\). At \(x = 0\), \(f'\) changes from negative to positive, so \(f\) has a local minimum. At \(x = 4\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. 2. The greatest slope of \(f\) is the maximum value of \(f'\). The vertex of the derivative graph is \((2, 2)\), so the greatest slope is \(2\) at \(x = 2\). 3. A line parallel to \(g\) must have slope \(1.5\). The graph shows \(f'(x) = 1.5\) at \(x = 1\) and \(x = 3\). 4. The vertex gives \(d = 2\) and \(c = 2\). Using \((0, 0)\), \(0 = a(0-2)^2 + 2\), so \(4a = -2\) and \(a = -0.5\).

Answer

a) Local minimum at \(x = 0\); local maximum at \(x = 4\) b) Greatest slope \(2\) at \(x = 2\) c) \(x = 1\) and \(x = 3\) d) \(a = -0.5\), \(d = 2\), and \(c = 2\)
53264012
Let \(f(x)=1.5\ln(x^2+1)+1\). The graph shows \(f\), \(f'\), and \(f''\), labeled a, b, and c. a) Match graphs a, b, and c with \(f\), \(f'\), and \(f''\). Justify your choices. b) Find the exact slope of \(f\) at \(x=2\). c) Find \(\lim_{x\to\pm\infty}f''(x)\) and state the horizontal asymptote of the graph of \(f''\).
Figure for problem 532640

Hints

- Compare zeros and extrema to test which graph could be the derivative of another. - The slope of \(f\) is read from \(f'\). - Compare numerator and denominator degrees for the end behavior of \(f''\).

Solution

1. Graph a represents \(f\). Its derivative is \(f'(x)=\frac{3x}{x^2+1}\), which is graph b. Differentiating again gives \(f''(x)=\frac{3-3x^2}{(x^2+1)^2}\), which is graph c. 2. The slope of \(f\) at \(x=2\) is \(f'(2)=\frac65\). 3. The denominator of \(f''\) has higher degree than its numerator, so \(f''(x)\to0\) as \(x\to\pm\infty\). The horizontal asymptote is \(y=0\).

Answer

a) a: \(f\); b: \(f'\); c: \(f''\). b) \(\frac65\). c) \(\lim_{x\to\pm\infty}f''(x)=0\); horizontal asymptote \(y=0\).
53264312
Panel a) shows the graph of \(f'\) on \(-2.5\le x\le2.5\). Panels b), c), and d) are candidate graphs for \(f\) on the same displayed interval. Which candidate graph is consistent with \(f'\)? Justify your choice from the sign of \(f'\). Then state the displayed intervals on which \(f\) is increasing or decreasing and give the x-coordinates of the local extrema indicated by the derivative sign changes.
Figure for problem 532643

Hints

- Read where the derivative graph is above and below the x-axis. - Translate positive derivative into increasing behavior and negative derivative into decreasing behavior. - Look for sign changes of the derivative before comparing the candidate function graphs.

Solution

1. In panel a), \(f'(x)>0\) for \(-2.5<x<-1\), \(f'(x)<0\) for \(-1<x<1\), and \(f'(x)>0\) for \(1<x<2.5\). 2. Therefore \(f\) must increase, then decrease, then increase across those three intervals. 3. Candidate b) has exactly that monotonicity pattern. Candidate c) has the opposite pattern, and candidate d) is increasing throughout the displayed interval. 4. Because \(f'\) changes from positive to negative at \(x=-1\), \(f\) has a local maximum there. Because \(f'\) changes from negative to positive at \(x=1\), \(f\) has a local minimum there.

Answer

Panel b) is consistent with \(f'\). \(f\) is increasing on \((-2.5,-1)\), decreasing on \((-1,1)\), and increasing on \((1,2.5)\). Local maximum x-coordinate: \(-1\). Local minimum x-coordinate: \(1\).
53264912
The graph of \(f'\) is shown. Determine whether each statement about \(f\) is true or false. Justify your answer. (1) \(f\) is strictly decreasing on \([-2,2]\). (2) \(f\) has a local maximum at \(x=2\). (3) The graph of \(f\) is concave up on \([0,3]\). (4) The graph of \(f\) has exactly two inflection points.
Figure for problem 532649

Hints

- Use the sign of \(f'\) for monotonicity and local extrema. - Use whether \(f'\) is increasing or decreasing for concavity. - Count changes in the direction of \(f'\), not merely zeros of \(f'\), when finding inflection points.

Solution

1. On \((-2,2)\), \(f'(x)<0\), so \(f\) is strictly decreasing. Statement (1) is true. 2. At \(x=2\), \(f'\) changes from negative to positive, so \(f\) has a local minimum, not a local maximum. Statement (2) is false. 3. On \((0,3)\), the graph of \(f'\) is increasing, so \(f\) is concave up. Statement (3) is true. 4. Inflection points of \(f\) occur where \(f'\) changes between decreasing and increasing. The parabola \(f'\) has only one extremum, at \(x=0\), so \(f\) has exactly one inflection point. Statement (4) is false.

Answer

(1) True. (2) False. (3) True. (4) False.
53265412
The graph shows the derivative \(f'\) of a polynomial function \(f\) on \([-4, 6]\). a) Find the intervals on which \(f\) is strictly increasing and strictly decreasing. b) Find the \(x\)-coordinates of all local extrema of \(f\), and classify each as a local minimum or local maximum. c) Does the graph of \(f\) have an inflection point? Justify your answer using the graph of \(f'\), and give its \(x\)-coordinate if it exists.
Figure for problem 532654

Hints

- Use the sign of \(f'\) to determine increasing and decreasing intervals. - Use the direction of each sign change to classify local extrema. - A local extremum of \(f'\) corresponds to a possible inflection point of \(f\).

Solution

1. The derivative is negative on \((-4, -1)\) and \((3, 6)\), so \(f\) is strictly decreasing on \([-4, -1]\) and \([3, 6]\). It is positive on \((-1, 3)\), so \(f\) is strictly increasing on \([-1, 3]\). 2. At \(x = -1\), \(f'\) changes from negative to positive, so \(f\) has a local minimum. At \(x = 3\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. 3. The graph of \(f'\) has a local maximum at \(x = 1\). Therefore, \(f''\) changes sign there, so \(f\) changes concavity and has an inflection point at \(x = 1\).

Answer

a) Increasing on \([-1, 3]\); decreasing on \([-4, -1]\) and \([3, 6]\) b) Local minimum at \(x = -1\); local maximum at \(x = 3\) c) Yes; the inflection point occurs at \(x = 1\).
53266212
The graph of a quadratic derivative \(g'\) is shown. Its vertex is \((1,-1.5)\), and its zeros are \(x=0\) and \(x=2\). a) Find the x-coordinates of all local extrema of \(g\), and classify each. b) The candidate function \(g(x)=0.5x^3-1.5x^2+2\) satisfies \(g(0)=2\). Differentiate it to verify the derivative graph, then calculate \(g(3)\).
Figure for problem 532662

Hints

- Use derivative sign changes to classify the two critical numbers. - Verify the candidate by differentiating rather than reconstructing it from the derivative. - Substitute \(x=3\) only after the candidate has been verified.

Solution

1. At \(x=0\), \(g'\) changes from positive to negative, so \(g\) has a local maximum. At \(x=2\), \(g'\) changes from negative to positive, so \(g\) has a local minimum. 2. Differentiating the candidate gives \(g'(x)=1.5x^2-3x\), which has zeros \(0\) and \(2\) and vertex \((1,-1.5)\), matching the graph. 3. \(g(3)=0.5(27)-1.5(9)+2=2\).

Answer

a) Local maximum at \(x=0\); local minimum at \(x=2\). b) \(g'(x)=1.5x^2-3x\), matching the graph, and \(g(3)=2\).
53267612
The three displayed graphs are labeled \(A\), \(B\), and \(C\). Match each graph with one function. 1) \(f(x)=(x-2)e^x\) 2) \(g(x)=3-e^x\) 3) \(h(x)=xe^{-x}\) Use each function's derivative together with intercepts and end behavior to justify the match.
Figure for problem 532676

Hints

- Calculate each y-intercept and find the zeros. - Differentiate each function and use the derivative sign to locate extrema. - Compare end behavior in both directions. - Match the resulting features with the displayed graphs.

Solution

1. For \(f(x)=(x-2)e^x\), \(f(0)=-2\), and the only zero is \(x=2\). Also, \(f'(x)=(x-1)e^x\), so \(f\) decreases for \(x<1\), increases for \(x>1\), and has a local minimum at \(x=1\). Since \(f(x)\to0\) as \(x\to-\infty\), these features match graph \(A\). 2. For \(g(x)=3-e^x\), \(g(0)=2\), \(g'(x)=-e^x<0\), so the function is strictly decreasing, and \(g(x)\to3\) as \(x\to-\infty\). These features match graph \(B\). 3. For \(h(x)=xe^{-x}\), the graph passes through \((0, 0)\). Since \(h'(x)=(1-x)e^{-x}\), it increases for \(x<1\), decreases for \(x>1\), and has a local maximum at \(x=1\). Also, \(h(x)\to0\) as \(x\to\infty\). These features match graph \(C\).

Answer

Graph \(A\): function 1; graph \(B\): function 2; graph \(C\): function 3.
53277912
The graph of a polynomial function \(f\) is shown. a) State the least possible degree of \(f\) and justify your answer from the graph. b) Use the graph's symmetry to write a general polynomial form of that least degree. c) Use the marked local maximum \(H\) and local minimum \(T\) to find an equation for \(f\).
Figure for problem 532779

Hints

- Read the coordinates of the marked local maximum and local minimum. - Count the turning points shown in the graph. - Relate the maximum possible number of turning points to polynomial degree. - Use origin symmetry to determine which powers may appear. - At the marked local minimum, use both the point and zero-slope conditions.

Solution

1. The graph has two local extrema. A degree-\(n\) polynomial can have at most \(n-1\) local extrema, so the least possible degree is \(3\). 2. The graph is symmetric about the origin, so a cubic of the least possible degree has the form \(f(x)=ax^3+cx\). 3. Using the local minimum \(T=(2,-4)\), the conditions \(f(2)=-4\) and \(f'(2)=0\) give \(4a+c=-2\) and \(12a+c=0\). Solving gives \(a=\frac14\) and \(c=-3\). Therefore, \(f(x)=\frac14x^3-3x\).

Answer

a) Degree \(3\) b) \(f(x)=ax^3+cx\) c) \(f(x)=\frac{1}{4}x^3-3x\)
53316412
The black graph is \(f'\). The graphs \(g\), \(h\), and \(k\) are candidates for the original function \(f\). Identify the graph of \(f\). Justify your choice using derivative signs, slopes, and critical points.
Figure for problem 533164

Hints

- Zeros of the derivative correspond to horizontal tangents of the original function. - Where \(f'>0\), \(f\) increases; where \(f'<0\), it decreases. - Eliminate candidates that fail either condition.

Solution

1. The derivative graph \(f'\) has zeros at \(x=-2\) and \(x=2\), so \(f\) must have horizontal tangents at those x-values. Graphs \(g\) and \(h\) do, while graph \(k\) does not. 2. On \((-2,2)\), \(f'(x)<0\), so \(f\) must be decreasing there. Graph \(g\) decreases on that interval, while graph \(h\) increases. 3. Therefore, graph \(g\) represents \(f\).

Answer

Graph \(g\) represents \(f\).
53369212
Figures 1 and 2 show a function \(g\) and its derivative \(g'\), but the figures are not labeled by role. a) Identify which figure is \(g\) and which is \(g'\). Justify your choice using horizontal tangents and derivative zeros. b) Find \(g(2)\). c) Find the slope of \(g\) at \(x=2\). d) Find \(g'(1)\). e) Give one value of \(x\) for which \(g(x)=1\). f) Find all \(x\)-values where \(g\) has a horizontal tangent. g) Give one \(x\)-value where the slope of \(g\) is \(3\).
Figure for problem 533692

Hints

- Identify the graph roles before reading any requested values. - Zeros of a derivative correspond to horizontal tangents of its function. - Once the derivative graph is identified, its y-values give tangent slopes of the function.

Solution

1. Figure 1 is \(g\), and Figure 2 is \(g'\). Figure 1 has horizontal tangents at \(x=-2,0,2\), exactly where Figure 2 crosses the x-axis. 2. Figure 1 gives \(g(2)=-3\). 3. The slope at \(x=2\) is \(g'(2)=0\). 4. Figure 2 gives \(g'(1)=-3\). 5. Figure 1 shows \(g(0)=1\), so \(x=0\) works. 6. Horizontal tangents occur where \(g'(x)=0\), at \(x=-2,0,2\). 7. Figure 2 shows \(g'(-1)=3\), so \(x=-1\) works.

Answer

a) Figure 1 is \(g\); Figure 2 is \(g'\). b) \(g(2)=-3\) c) \(0\) d) \(-3\) e) \(x=0\) f) \(x=-2,0,2\) g) \(x=-1\)
53370012
The graph of a periodic function \(f\) is shown. 1) Within the displayed interval, find all inputs where the graph of \(f'\) crosses the x-axis. 2) At what input in \([-4,4]\) does \(f'\) appear to reach its greatest value? Justify your answer using the steepness of \(f\).
Figure for problem 533700

Hints

- Locate the local maximum and local minimum of \(f\). - The derivative is zero at horizontal tangent lines. - Look for the point where the graph rises most steeply.

Solution

1. The derivative is zero at the local extrema of \(f\). The graph has a local minimum at \(x=-\frac{\pi}{2}\) and a local maximum at \(x=\frac{\pi}{2}\). Therefore, the graph of \(f'\) crosses the x-axis at those two inputs. 2. The derivative is greatest where the graph of \(f\) rises most steeply. This occurs at the origin, so \(f'\) reaches its greatest value at \(x=0\).

Answer

1) \(x=-\frac{\pi}{2}\) and \(x=\frac{\pi}{2}\) 2) \(x=0\)
53370912
The figure shows two functions, \(p\) and \(q\). One graph is the derivative of the other. a) Decide which graph represents the function and which represents its derivative. Justify your answer using the relationship between local extrema and zeros. b) Use the graph to estimate \(p(2)\) and \(p'(2)\).
Figure for problem 533709

Hints

- A smooth local maximum or minimum occurs where the derivative is zero. - Read \(p(2)\) from the graph of \(p\) and \(p'(2)\) from the derivative graph.

Solution

1. The graph of \(p\) has a local maximum at \(x = -1\) and a local minimum at \(x = 3\). The graph of \(q\) is zero at those same \(x\)-values. Therefore, \(q = p'\). 2. Reading from the graph of \(p\), \(p(2) \approx -0.4\). 3. Since \(q = p'\), \(p'(2) = q(2) \approx -1.8\).

Answer

a) \(q\) is the derivative of \(p\), so \(q = p'\). b) \(p(2) \approx -0.4\) and \(p'(2) \approx -1.8\)
53377212
The graph shown is the derivative \(f'\) of a function \(f\). Determine whether each statement is true or false, and justify your answer from the graph. 1) The function \(f\) has exactly two inflection points on \([-3, 3]\). 2) The graph of \(f\) is concave down on \([0, 2]\). 3) \(f(2)<f(3)\). 4) The function \(f\) has a local minimum at \(x=0\).
Figure for problem 533772

Hints

- Local extrema of \(f'\) correspond to inflection points of \(f\). - The monotonicity of \(f'\) determines the concavity of \(f\). - What does a positive derivative imply when comparing two function values? - Use the sign change of \(f'\) to classify a critical number of \(f\).

Solution

1. Statement 1 is true. The graph of \(f'\) has two local extrema on \([-3, 3]\), so \(f\) has two inflection points. 2. Statement 2 is false. The derivative \(f'\) decreases only until \(x=\frac{2}{\sqrt{3}}\approx1.15\), then increases. Therefore, \(f\) is not concave down on the entire interval \([0, 2]\). 3. Statement 3 is true. Since \(f'(x)>0\) for \(2<x<3\), the function \(f\) is increasing there. Therefore, \(f(2)<f(3)\). 4. Statement 4 is false. At \(x=0\), \(f'\) changes from positive to negative, so \(f\) has a local maximum, not a local minimum.

Answer

1) True 2) False 3) True 4) False
53377712
The graph shown is the derivative \(f'\) of a function \(f\). Determine whether each statement is true or false, and justify your answer. a) The function \(f\) is strictly decreasing on \([1, 3]\). b) The graph of \(f\) has a local maximum at \(x=1\). c) The graph of \(f\) is concave up at \(x=0\).
Figure for problem 533777

Hints

- Use the sign of \(f'\) to determine whether \(f\) is increasing or decreasing. - Use sign changes of \(f'\) to classify critical points of \(f\). - The monotonicity of \(f'\) determines the concavity of \(f\).

Solution

1. Statement a is true. On \((1, 3)\), \(f'(x)<0\), with zeros at the endpoints. Therefore, \(f\) is strictly decreasing on \([1, 3]\). 2. Statement b is true. At \(x=1\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. 3. Statement c is false. At \(x=0\), the graph of \(f'\) is decreasing, so \(f''(0)<0\). Therefore, \(f\) is concave down there.

Answer

a) True b) True c) False
53379112
Let \(f(x)=\frac{1}{4}x^4-2x^2+4\). Find the exact coordinates of the marked zeros \(N_1\) and \(N_2\), the marked local maximum \(H\), and both inflection points \(W_1\) and \(W_2\).
Figure for problem 533791

Hints

- Factor the polynomial to find its zeros. - Use the first and second derivatives to find the local maximum. - Set the second derivative equal to \(0\) for possible inflection points. - Use the graph's symmetry to check paired answers.

Solution

1. Since \(f(x)=\frac{1}{4}(x^2-4)^2\), the zeros are \(x=-2\) and \(x=2\), each with multiplicity \(2\). Thus, \(N_1=(-2, 0)\) and \(N_2=(2, 0)\). 2. The derivatives are \(f'(x)=x^3-4x\), \(f''(x)=3x^2-4\), and \(f'''(x)=6x\). The second-derivative test gives a local maximum at \(H=(0, 4)\). 3. Solving \(f''(x)=0\) gives \(x=\pm\frac{2\sqrt{3}}{3}\). At either value, \(f(x)=\frac{16}{9}\), and the third derivative is nonzero. Therefore, \(W_1=(-\frac{2\sqrt{3}}{3}, \frac{16}{9})\) and \(W_2=(\frac{2\sqrt{3}}{3}, \frac{16}{9})\).

Answer

\(N_1=(-2, 0)\), \(N_2=(2, 0)\), \(H=(0, 4)\), \(W_1=(-\frac{2\sqrt{3}}{3}, \frac{16}{9})\), and \(W_2=(\frac{2\sqrt{3}}{3}, \frac{16}{9})\)
53379212
Let \(f(x)=x^3-6x^2+9x\). Find all zeros, the local maximum \(H\), the local minimum \(T\), and the inflection point \(W\). Compare your results with the graph.
Figure for problem 533792

Hints

- Factor the polynomial to find zeros and multiplicities. - Use the first and second derivatives for extrema. - Use the second derivative for the inflection point. - Compare each coordinate with the graph.

Solution

1. Factoring gives \(f(x)=x(x-3)^2\). Therefore, \(x=0\) is a simple zero and \(x=3\) is a double zero. 2. The derivatives are \(f'(x)=3(x-1)(x-3)\), \(f''(x)=6x-12\), and \(f'''(x)=6\). The second-derivative test gives a local maximum at \(H=(1, 4)\) and a local minimum at \(T=(3, 0)\). 3. Solving \(f''(x)=0\) gives \(x=2\), and \(f(2)=2\). Thus, \(W=(2, 2)\). All points agree with the graph.

Answer

Zeros: \((0, 0)\), simple, and \((3, 0)\), double; local maximum: \(H=(1, 4)\); local minimum: \(T=(3, 0)\); inflection point: \(W=(2, 2)\) All points agree with the graph.
53380012
The graph shows the derivative \(f'\) of a function \(f\). a) Find the \(x\)-coordinates of all local extrema of \(f\) in the displayed interval. Classify each as a local maximum or local minimum, and justify your answer using the sign changes of \(f'\). b) Find the interval or intervals on which \(f\) is strictly decreasing. c) How many inflection points does \(f\) have for \(-4 < x < 6\)? Justify your answer using the graph of \(f'\).
Figure for problem 533800

Hints

- Use zeros and sign changes of \(f'\) to identify local extrema. - The function decreases where its derivative is negative. - Inflection points of \(f\) correspond to local extrema of \(f'\).

Solution

1. The derivative is zero at \(x = -3\), \(x = 1\), and \(x = 5\). 2. At \(x = -3\), \(f'\) changes from negative to positive, so \(f\) has a local minimum. At \(x = 1\), it changes from positive to negative, so \(f\) has a local maximum. At \(x = 5\), it changes from negative to positive, so \(f\) has a local minimum. 3. The derivative is negative on \((-4, -3)\) and \((1, 5)\), so \(f\) is strictly decreasing on \([-4, -3]\) and \([1, 5]\). 4. Inflection points of \(f\) occur where \(f'\) has local extrema. The derivative graph has exactly two local extrema in the displayed interval, so \(f\) has two inflection points.

Answer

a) Local minima at \(x = -3\) and \(x = 5\); local maximum at \(x = 1\) b) \([-4, -3]\) and \([1, 5]\) c) Two inflection points
53380712
Let \(f(x)=\frac{1}{3}x^3-x\). The four panels show the graphs of \(f\), its derivative \(f'\), and the transformed functions \(g(x)=f(x)+2\) and \(h(x)=f(x-2)\). Match graphs I through IV to the four functions.
Figure for problem 533807

Hints

- Compare the general shapes of a cubic function and its derivative. - The derivative is zero where the original graph has horizontal tangents. - Adding a constant outside a function shifts its graph vertically. - Replacing \(x\) with \(x-c\) shifts a graph horizontally.

Solution

1. Differentiate: \(f'(x)=x^2-1\). This is an upward-opening parabola with vertex \((0, -1)\) and zeros at \(x=-1\) and \(x=1\), so it is graph I. 2. The original function \(f\) is the cubic with a local maximum at \((-1, \frac{2}{3})\) and a local minimum at \((1, -\frac{2}{3})\), so it is graph II. 3. The function \(h(x)=f(x-2)\) shifts the graph of \(f\) right \(2\) units, so it is graph III. 4. The function \(g(x)=f(x)+2\) shifts the graph of \(f\) up \(2\) units, so it is graph IV.

Answer

I: \(f^{\prime}(x)\); II: \(f(x)\); III: \(h(x)=f(x-2)\); IV: \(g(x)=f(x)+2\).
53381512
The graph shows the derivative \(f'\) of a function \(f\). Determine whether each statement is true or false, and briefly justify your answer. a) The graph of \(f\) has a local maximum at \(x = 0\). b) The function \(f\) is strictly decreasing on \([0, 4]\). c) The graph of \(f\) has an inflection point at \(x = 2\).
Figure for problem 533815

Hints

- Use zeros and sign changes of \(f'\) to identify local extrema. - The function decreases where \(f' < 0\). - A local extremum of \(f'\) indicates a possible inflection point of \(f\).

Solution

1. At \(x = 0\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. Statement a) is true. 2. For \(0 < x < 4\), \(f'(x) < 0\), so \(f\) is strictly decreasing on \([0, 4]\). Statement b) is true. 3. The graph of \(f'\) has a local minimum at \(x = 2\), so \(f''\) changes sign there. Therefore, \(f\) changes concavity and has an inflection point at \(x = 2\). Statement c) is true.

Answer

a) True b) True c) True
53384612
The graph shown is the first derivative \(f'\) of a polynomial function \(f\) on \(-1\le x\le5\). Determine whether each statement is true or false. a) The graph of \(f\) is concave up for \(2<x\le5\). b) The function \(f\) has a local maximum at \(x=4\). c) The function \(f\) has an inflection point at \(x=2\). d) The function \(f\) is strictly decreasing on \([0, 2]\).
Figure for problem 533846

Hints

- The monotonicity of \(f'\) determines the concavity of \(f\). - Use sign changes of \(f'\) to identify local extrema of \(f\). - Local extrema of \(f'\) correspond to inflection points of \(f\). - Use the sign of \(f'\) to determine whether \(f\) increases or decreases.

Solution

1. Statement a is false. For \(x>2\), the graph of \(f'\) is decreasing, so \(f''(x)<0\) and \(f\) is concave down. 2. Statement b is true. At \(x=4\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. 3. Statement c is true. The graph of \(f'\) has a local maximum at \(x=2\), so the concavity of \(f\) changes there. 4. Statement d is false. For \(0<x<2\), \(f'(x)>0\), so \(f\) is strictly increasing there.

Answer

a) False b) True c) True d) False
53390212
The graph of a function \(f\) is shown; no algebraic formula for \(f\) is given. Focus on the branch for \(x>0\). Describe the graph of \(f'\) on this branch: state its sign, whether its values increase or decrease as \(x\) increases, and the value that \(f'(x)\) approaches as \(x\to\infty\). Explain each conclusion from the changing tangent slopes of \(f\).
Figure for problem 533902

Hints

- Use only the displayed shape; no formula for \(f\) is available. - Decide the sign of tangent slopes on the right-hand branch. - Compare how steep the graph is at smaller and larger positive x-values. - Consider what happens to tangent slopes as the graph becomes nearly horizontal.

Solution

1. On the branch for \(x>0\), the graph rises as \(x\) increases, so its tangent slopes are positive. Thus \(f'(x)>0\). 2. The graph becomes progressively flatter, so the positive tangent slopes decrease as \(x\) increases. Therefore, the graph of \(f'\) decreases while remaining above the x-axis. 3. The graph approaches a horizontal level, so its tangent slopes approach \(0\). Hence \(f'(x)\to0\) from above as \(x\to\infty\).

Answer

For \(x>0\), \(f'(x)>0\), the derivative values decrease as \(x\) increases, and \(f'(x)\to0\) from above as \(x\to\infty\).
53391512
The graph of the derivative \(f^{\prime}\) is shown on \([-4, 4]\). Use the graph to answer the following questions about \(f\) on the displayed interval. 1. Find the x-coordinates of all local extrema of \(f\), and classify each as a local maximum or local minimum. 2. On what intervals is \(f\) strictly decreasing? 3. At what x-values does \(f\) have inflection points? Briefly justify your answer.
Figure for problem 533915

Hints

- Zeros and sign changes of \(f^{\prime}\) determine local extrema of \(f\). - The function \(f\) decreases where \(f^{\prime}<0\). - Inflection points of \(f\) occur where \(f^{\prime}\) changes monotonicity.

Solution

1. Local extrema of \(f\) occur where \(f^{\prime}\) changes sign. The graph has zeros at approximately \(x=-2.4\), \(x=0\), and \(x=2.4\). The sign changes from negative to positive at \(x\approx-2.4\), so \(f\) has a local minimum there. It changes from positive to negative at \(x=0\), so \(f\) has a local maximum there. It changes from negative to positive at \(x\approx2.4\), so \(f\) has a local minimum there. 2. The function \(f\) is strictly decreasing where \(f^{\prime}<0\), which on the displayed interval is approximately \((-4, -2.4)\) and \((0, 2.4)\). 3. Inflection points of \(f\) occur where \(f^{\prime}\) changes from increasing to decreasing or from decreasing to increasing. The graph of \(f^{\prime}\) has local extrema at approximately \(x=-1.4\) and \(x=1.4\), so those are the inflection-point x-values of \(f\).

Answer

1. Local minima at \(x\approx-2.4\) and \(x\approx2.4\); local maximum at \(x=0\) 2. Approximately \((-4, -2.4)\) and \((0, 2.4)\) 3. Approximately \(x=-1.4\) and \(x=1.4\)
53392112
Match each function graph, (1), (2), and (3), with its derivative graph, (A), (B), or (C). Explain your choices using features such as local extrema, zeros, and increasing and decreasing behavior.
Figure for problem 533921

Hints

- Match local extrema with zeros of the derivative. - Compare increasing and decreasing intervals with the sign of the derivative. - Use the degree and symmetry of each graph as a check.

Solution

1. Graph (1) has local minima at \(x=-2\) and \(x=2\) and a local maximum at \(x=0\). Its derivative must be zero at \(-2\), \(0\), and \(2\), so (1) matches (B). 2. Graph (2) is \(2\sin x\). Its derivative is \(2\cos x\), so (2) matches (C). 3. Graph (3) is a downward-opening parabola with vertex at \(x=0\). Its derivative is a decreasing line through the origin, so (3) matches (A).

Answer

(1) \(\rightarrow\) (B); (2) \(\rightarrow\) (C); (3) \(\rightarrow\) (A).
53392212
Which graph, (A), (B), or (C), is the derivative of each function graph, (1), (2), and (3)? Match the pairs and justify your choices.
Figure for problem 533922

Hints

- Match local extrema with zeros of the derivative. - Compare increasing and decreasing behavior with the sign of the derivative. - Consider behavior near asymptotes and at the edges of the displayed interval.

Solution

1. Graph (1) is \(e^x - 2\), which is increasing everywhere. Its derivative is \(e^x\), which is always positive, so (1) matches (A). 2. Graph (2) is \(\frac{1}{x}\), which decreases on both parts of its domain. Its derivative is \(-\frac{1}{x^2}\), which is always negative, so (2) matches (C). 3. Graph (3) has a local maximum at \(x = -1\) and a local minimum at \(x = 1\). Its derivative must be an upward-opening parabola with zeros at \(x = -1\) and \(x = 1\), so (3) matches (B).

Answer

(1) \(\rightarrow\) (A); (2) \(\rightarrow\) (C); (3) \(\rightarrow\) (B).
53395312
Determine whether the graph of \(f(x)=x^3-3x^2\) correctly shows all key features. Find the intercepts, local extrema, and inflection point exactly, and compare them with the diagram.
Figure for problem 533953

Hints

- Factor the polynomial to find x-intercepts and multiplicities. - Use the first and second derivatives to find and classify extrema. - Use the second derivative to find the inflection point. - Compare the exact coordinates with the graph.

Solution

1. Since \(f(x)=x^2(x-3)\), the x-intercepts are \((0, 0)\), with multiplicity \(2\), and \((3, 0)\), with multiplicity \(1\). The y-intercept is also \((0, 0)\). 2. The derivatives are \(f'(x)=3x(x-2)\), \(f''(x)=6x-6\), and \(f'''(x)=6\). The second-derivative test gives a local maximum at \((0, 0)\) and a local minimum at \((2, -4)\). 3. The inflection point occurs at \(x=1\), where \(f(1)=-2\). Thus, the inflection point is \((1, -2)\). 4. These exact points agree with the diagram, so the graph is correct.

Answer

Yes, the graph is correct. Intercepts: \((0, 0)\), a double x-intercept and the y-intercept; \((3, 0)\), a simple x-intercept Local maximum: \((0, 0)\); local minimum: \((2, -4)\) Inflection point: \((1, -2)\)
53395412
Determine whether the displayed graph correctly represents \(f(x)=-x^3+3x+2\). Find all intercepts and local extrema exactly to justify your conclusion.
Figure for problem 533954

Hints

- Evaluate the function at \(x=0\). - Factor the cubic to find zeros and multiplicities. - Use the first and second derivatives to find and classify extrema. - Compare the exact values with the graph's scale.

Solution

1. The y-intercept is \((0, 2)\). Factoring gives \(f(x)=-(x+1)^2(x-2)\), so the x-intercepts are \((-1, 0)\), with multiplicity \(2\), and \((2, 0)\), with multiplicity \(1\). 2. The derivatives are \(f'(x)=-3x^2+3\) and \(f''(x)=-6x\). The critical numbers are \(x=-1\) and \(x=1\). The second-derivative test gives a local minimum at \((-1, 0)\) and a local maximum at \((1, 4)\). 3. The displayed graph has y-intercept \((0, 1.6)\) and a local maximum near \((1, 3.2)\). These do not match the exact values, so the graph is incorrect.

Answer

No. Intercepts: \((0, 2)\), \((-1, 0)\) with multiplicity \(2\), and \((2, 0)\) Local minimum: \((-1, 0)\); local maximum: \((1, 4)\)
53395612
Let \(f(x)=\frac{1}{4}x^4-x^3+2\). Determine whether the displayed graph correctly shows the function's key features, and find those features exactly.
Figure for problem 533956

Hints

- Check \(f(0)\) before doing further calculations. - Find the zeros of the first derivative; if the first and second derivatives are both \(0\), check the third derivative. - Compute the exact stationary-point coordinates and compare them with the graph.

Solution

1. The y-intercept is \((0, 2)\), but the displayed graph has y-intercept \((0, 4)\). This already shows that the graph is incorrect. 2. The derivative is \(f'(x)=x^2(x-3)\). Thus, the critical numbers are \(x=0\) and \(x=3\). 3. At \(x=3\), \(f''(3)=9>0\), so there is a local minimum at \((3, -\frac{19}{4})\). At \(x=0\), the first and second derivatives are \(0\), while \(f'''(0)=-6\ne0\), so \((0, 2)\) is a stationary inflection point. 4. These points do not match the displayed graph, so the graph is incorrect.

Answer

No. Y-intercept and stationary inflection point: \((0, 2)\) Local minimum: \((3, -\frac{19}{4})\)
53395812
Determine whether the graph of \(f(x)=x^3-3x^2+4\) is displayed correctly. Find the intercepts, local extrema, and inflection point exactly to justify your answer.
Figure for problem 533958

Hints

- Find the critical numbers from the first derivative and classify them with the second derivative. - A local minimum on the x-axis is a multiple zero. - Set the second derivative equal to \(0\) to locate the inflection point. - Compare the exact critical numbers and inflection-point location with the graph.

Solution

1. The y-intercept is \((0,4)\). The derivative is \(f'(x)=3x(x-2)\), so the critical numbers are \(x=0\) and \(x=2\). 2. Since \(f''(0)=-6<0\), \((0,4)\) is a local maximum. Since \(f''(2)=6>0\), \((2,0)\) is a local minimum. 3. Because the local minimum lies on the x-axis, \(x=2\) is a double zero. Factoring gives \(f(x)=(x-2)^2(x+1)\), so the other x-intercept is \((-1,0)\). 4. Solving \(f''(x)=6x-6=0\) gives \(x=1\). Since \(f(1)=2\), the inflection point is \((1,2)\). 5. The displayed graph places the local minimum at \(x=3\), not \(x=2\), and its inflection point is also misplaced. Therefore, it is incorrect.

Answer

No. Intercepts: \((0,4)\), \((-1,0)\), and \((2,0)\), where \(x=2\) is a double zero Local maximum: \((0,4)\); local minimum: \((2,0)\) Inflection point: \((1,2)\)
53395912
Panels a) and b) show two functions, \(f_1\) and \(f_2\). Panel c) shows three possible derivative graphs, \(g_1\), \(g_2\), and \(g_3\). 1. Match \(f_1\) and \(f_2\) with their derivative graphs from panel c). 2. Justify the match for \(f_1\) using the slope behavior of its graph. 3. Find the interval on which \(f_1\) is strictly decreasing.
Figure for problem 533959

Hints

- Match local extrema of a function with zeros of its derivative. - Compare increasing and decreasing intervals with the sign of the derivative. - Use the function types and polynomial degrees as a check.

Solution

1. The function \(f_1\) matches \(g_1\), and \(f_2\) matches \(g_2\). 2. The graph of \(f_1\) has a local maximum at \(x = -2\) and a local minimum at \(x = 2\). Graph \(g_1\) is zero at those values. Between them, \(f_1\) decreases, and \(g_1\) is negative. 3. Therefore, \(f_1\) is strictly decreasing on \([-2, 2]\).

Answer

1. \(f_1 \rightarrow g_1\); \(f_2 \rightarrow g_2\) 2. The zeros and sign of \(g_1\) match the horizontal tangents and monotonicity of \(f_1\). 3. \([-2, 2]\)
53397212
The figure shows a function \(f\) (blue) and its first derivative \(f'\) (red). a) Explain why the color assignment is correct based on the shapes and behavior of the graphs. b) Find the \(x\)-coordinates of the local extrema of \(f\), and classify each as a local maximum or local minimum. c) Estimate the coordinates of the inflection point of \(f\) to the nearest tenth.
Figure for problem 533972

Hints

- Compare the polynomial degrees. - Match zeros of the derivative with horizontal tangents of the function. - The \(x\)-coordinate of an inflection point of \(f\) corresponds to a local extremum of \(f'\).

Solution

1. The blue graph is cubic and the red graph is quadratic, consistent with differentiation lowering the degree by one. Also, the zeros of the red graph occur at the horizontal tangents of the blue graph. Therefore, blue represents \(f\), and red represents \(f'\). 2. The derivative is zero at \(x = -1\) and \(x = 2\). At \(x = -1\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. At \(x = 2\), it changes from negative to positive, so \(f\) has a local minimum. 3. The vertex of the derivative graph is at \(x = 0.5\), so \(f\) changes concavity there. Reading the blue graph to the nearest tenth gives \(f(0.5) \approx 0.4\), so the inflection point is approximately \((0.5, 0.4)\).

Answer

a) Blue represents \(f\), and red represents \(f'\). b) Local maximum at \(x = -1\); local minimum at \(x = 2\) c) Approximately \((0.5, 0.4)\)
53397612
The graph of \(f(x)=-\frac{1}{2}x^3+3x-1\) is shown. a) Determine the number of real zeros from the graph. Explain why a cubic polynomial can have at most three real zeros. b) Identify the number of local extrema and state the end behavior. c) Explain without calculation why the graph must have an inflection point between the two extrema.
Figure for problem 533976

Hints

- Count the x-axis crossings. - Use the polynomial degree to bound the number of zeros. - Identify the graph's local maximum and local minimum. - Use the sign and degree of the leading term for end behavior. - Relate the two extrema to the shape of the quadratic derivative.

Solution

1. The graph crosses the x-axis three times, so \(f\) has three real zeros. A degree-\(3\) polynomial can have at most three real zeros because a nonzero polynomial cannot have more zeros than its degree. 2. The graph has two local extrema. Since the leading term is \(-\frac{1}{2}x^3\), \(f(x)\to-\infty\) as \(x\to\infty\), and \(f(x)\to\infty\) as \(x\to-\infty\). 3. The derivative is a quadratic with two distinct zeros at the extrema. Its vertex lies between those zeros, where the derivative changes from decreasing to increasing or vice versa. Therefore, the second derivative changes sign there, producing an inflection point between the extrema.

Answer

a) Three real zeros; a cubic has at most three real zeros. b) Two local extrema; \(f(x)\to-\infty\) as \(x\to\infty\), and \(f(x)\to\infty\) as \(x\to-\infty\). c) The quadratic derivative has its vertex between its two zeros, so the second derivative changes sign there.
53398612
The graph of the derivative \(f^{\prime}\) is shown. 1. Describe the key features of one possible graph of \(f\), including its local extrema and inflection point. 2. Describe where \(f\) is increasing and decreasing on \([-3, 5]\).
Figure for problem 533986

Hints

- Zeros of \(f^{\prime}\) give locations of horizontal tangents on \(f\). - Where \(f^{\prime}>0\), \(f\) increases. - Where \(f^{\prime}<0\), \(f\) decreases. - Where \(f^{\prime}\) changes from increasing to decreasing, \(f\) changes concavity.

Solution

1. The derivative is \(0\) at \(x=-2\) and \(x=4\). It changes from negative to positive at \(x=-2\), so a possible graph of \(f\) has a local minimum there. It changes from positive to negative at \(x=4\), so the graph has a local maximum there. The graph of \(f^{\prime}\) increases up to \(x=1\) and decreases after \(x=1\), so \(f\) changes from concave up to concave down and has an inflection point at \(x=1\). Any vertical shift with these slope and concavity properties is acceptable. 2. Since \(f^{\prime}<0\) on \((-3, -2)\), \(f\) is decreasing there. Since \(f^{\prime}>0\) on \((-2, 4)\), \(f\) is increasing there. Since \(f^{\prime}<0\) on \((4, 5)\), \(f\) is decreasing there.

Answer

1. One possible graph has a local minimum at \(x=-2\), an inflection point at \(x=1\), and a local maximum at \(x=4\), with slopes matching the displayed derivative. 2. Decreasing on \((-3, -2)\) and \((4, 5)\); increasing on \((-2, 4)\)
53398712
The graph of the derivative \(f^{\prime}\) is shown on \([-2, 5]\). 1. Describe the key features of one possible graph of \(f\) on the displayed interval. 2. At \(x=3\), the graph of \(f^{\prime}\) touches the x-axis without changing sign. What special feature does the graph of \(f\) have there? Briefly justify your answer.
Figure for problem 533987

Hints

- A zero of the derivative without a sign change does not produce a local extremum. - Use whether \(f^{\prime}\) is increasing or decreasing to determine the concavity of \(f\). - Determine whether \(f^{\prime}\) is increasing or decreasing on each side of \(x=3\). - A horizontal tangent together with a change in concavity indicates a stationary inflection point.

Solution

1. The derivative changes from negative to positive at \(x=0\), so a possible graph of \(f\) has a local minimum at \(x=0\). The graph of \(f^{\prime}\) increases up to \(x=1\), decreases from \(x=1\) to \(x=3\), and increases after \(x=3\). Therefore, \(f\) is concave up, then concave down, then concave up, with inflection points at \(x=1\) and \(x=3\). At \(x=3\), \(f^{\prime}=0\), but \(f^{\prime}\) is positive on both sides, so \(f\) remains increasing and has no local extremum there. 2. The graph of \(f^{\prime}\) has a local minimum at \(x=3\). Therefore, \(f^{\prime}\) changes from decreasing to increasing, so the concavity of \(f\) changes. Because \(f^{\prime}(3)=0\), \(f\) has a stationary inflection point at \(x=3\).

Answer

1. One possible graph has a local minimum at \(x=0\), an inflection point at \(x=1\), and a stationary inflection point at \(x=3\); it remains increasing through \(x=3\). 2. At \(x=3\), \(f\) has a stationary inflection point: its tangent is horizontal, but the function remains increasing through the point.
53398812
The graph shown is \(f'\) on \([-3,1]\). Give a text-only graph blueprint for \(f\) on that interval. a) State the maximal intervals on which \(f\) is increasing and decreasing. b) Classify each horizontal tangent of \(f\) shown by a zero of \(f'\). c) Use the local extrema of the graph of \(f'\) to identify the inflection-point x-coordinates of \(f\); give the noninteger value to the nearest tenth. d) At what x-value does \(f\) attain its greatest value on \([-3,1]\)?
Figure for problem 533988

Hints

- The sign of \(f'\) gives the direction of the original function. - A zero of \(f'\) that merely touches the x-axis behaves differently from a sign-changing zero. - Local extrema of \(f'\) correspond to changes in the concavity of \(f\). - Use the monotonicity on the full displayed interval to determine where the greatest value occurs.

Solution

1. The graph of \(f'\) is positive on \((-3,0)\) except that it touches \(0\) at \(x=-2\), and it is negative on \((0,1)\). Therefore, \(f\) is increasing on \((-3,0)\) and decreasing on \((0,1)\). 2. At \(x=-2\), \(f'\) is zero but does not change sign, so the horizontal tangent is not an extremum. Because \(f'\) has a local minimum there, the concavity of \(f\) changes, making \(x=-2\) a stationary-inflection input. At \(x=0\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. 3. The graph of \(f'\) has local extrema at \(x=-2\) and approximately \(x=-0.7\). Therefore, \(f\) has inflection points at those x-values. 4. Since \(f\) increases up to \(x=0\) and decreases afterward, its greatest value on the displayed interval occurs at \(x=0\).

Answer

a) Increasing on \((-3,0)\); decreasing on \((0,1)\). b) \(x=-2\): stationary inflection point; \(x=0\): local maximum. c) Inflection-point x-coordinates: \(-2\) and approximately \(-0.7\). d) \(x=0\).
53398912
The graph of the derivative \(f^{\prime}\) is shown on \([-4, 3]\). 1. Describe the key features of one possible graph of \(f\) on the displayed interval. 2. Find every x-value where the tangent to \(f\) is horizontal. Classify each point as a local maximum, a local minimum, or a stationary inflection point, and justify your classifications.
Figure for problem 533989

Hints

- Find the zeros of \(f^{\prime}\). - Use the sign of \(f^{\prime}\) on each interval to determine whether \(f\) increases or decreases. - A sign change at a zero indicates a local extremum. - Turning points of \(f^{\prime}\) indicate changes in the concavity of \(f\).

Solution

1. The zeros of \(f^{\prime}\) are \(x=-3\), \(x=-1\), and \(x=2\). These are the x-values where \(f\) has horizontal tangents. The graph of \(f^{\prime}\) has a local maximum at approximately \(x=-2.1\) and a local minimum at approximately \(x=0.8\), so a corresponding graph of \(f\) changes concavity at those x-values. Any vertical shift with these slope and concavity properties is possible. 2. At \(x=-3\), \(f^{\prime}\) changes from negative to positive, so \(f\) has a local minimum. At \(x=-1\), it changes from positive to negative, so \(f\) has a local maximum. At \(x=2\), it changes from negative to positive, so \(f\) has a local minimum. There are no stationary inflection points because the derivative changes sign at every zero.

Answer

1. One possible graph has local minima at \(x=-3\) and \(x=2\), a local maximum at \(x=-1\), and inflection points at approximately \(x=-2.1\) and \(x=0.8\). 2. Horizontal tangents occur at \(x=-3\) (local minimum), \(x=-1\) (local maximum), and \(x=2\) (local minimum). There are no stationary inflection points.
53399512
Find a function of the form \(f(x)=ax^3+bx+c\) that matches the displayed graph.
Figure for problem 533995

Hints

- Use the inflection point on the y-axis to find the constant term. - At a marked local extremum, use both its coordinates and the condition that the derivative is \(0\).

Solution

1. The graph's inflection point is \((0, 1)\), so \(c=1\). 2. The graph has a local maximum at \((-1, 3)\) and a local minimum at \((1, -1)\). Since \(f'(x)=3ax^2+b\), the zero slope at \(x=1\) gives \(3a+b=0\), so \(b=-3a\). 3. Using \(f(1)=-1\), \(a-3a+1=-1\), so \(a=1\) and \(b=-3\). 4. Therefore, \(f(x)=x^3-3x+1\).

Answer

\(f(x)=x^3-3x+1\)
53400012
The graph shown is the first derivative \(f'\) of a function \(f\). a) Find the x-coordinates of the inflection points of \(f\). Explain the relationship you use. b) Determine the intervals in the displayed window where the graph of \(f\) is concave down.
Figure for problem 534000

Hints

- At an inflection point of \(f\), the slope represented by \(f'\) changes from increasing to decreasing or vice versa. - Where does the graph of \(f'\) have local maxima or minima? - How does the monotonicity of \(f'\) determine the concavity of \(f\)? - Concave-down behavior occurs where \(f'\) is decreasing.

Solution

1. Inflection points of \(f\) occur where \(f'\) has local extrema, because the monotonicity of \(f'\) changes there. 2. The graph of \(f'\) has local extrema at \(x=-2\), \(x=0\), and \(x=2\). Therefore, these are the x-coordinates of the inflection points of \(f\). 3. The displayed x-range is \([-3,4]\). The graph of \(f'\) is decreasing on \([-3,-2)\) and \((0,2)\), so \(f\) is concave down on those intervals.

Answer

a) \(x=-2\), \(x=0\), and \(x=2\) b) \([-3, -2)\) and \((0, 2)\)
53401112
Analyze \(f(x)=\frac12x^3-6x\). a) Find all intercepts, local extrema, and the inflection point. b) Give a text-only graph blueprint: state the maximal monotonicity and concavity intervals, then list the extrema and inflection point in left-to-right order with the end behavior.

Hints

- Factor first to get the intercepts efficiently. - Use the zeros and signs of \(f'\) to organize the monotonicity pieces. - Use the sign of \(f''\) to organize the concavity pieces and locate the inflection point. - The leading cubic term determines the two ends of the blueprint.

Solution

1. Factoring gives \(f(x)=\frac12x(x^2-12)\). The x-intercepts are \((0,0)\) and \((\pm2\sqrt3,0)\). 2. \(f'(x)=\frac32x^2-6\), so the critical numbers are \(x=\pm2\). Since \(f''(x)=3x\), the second derivative test gives a local maximum at \((-2,8)\) and a local minimum at \((2,-8)\). 3. The second derivative changes sign at \(x=0\), so \((0,0)\) is the inflection point. 4. The graph increases on \(( -\infty,-2)\), decreases on \((-2,2)\), and increases on \((2,\infty)\). It is concave down on \(( -\infty,0)\) and concave up on \((0,\infty)\). 5. Because the leading term is positive cubic, the left end goes to \(-\infty\) and the right end goes to \(\infty\). These facts determine the requested blueprint.

Answer

a) Intercepts: \((0,0)\), \((\pm2\sqrt3,0)\). Local maximum: \((-2,8)\). Local minimum: \((2,-8)\). Inflection point: \((0,0)\). b) Increasing on \(( -\infty,-2)\), decreasing on \((-2,2)\), increasing on \((2,\infty)\); concave down for \(x<0\), concave up for \(x>0\). Left-to-right: left end down → maximum \((-2,8)\) → inflection \((0,0)\) → minimum \((2,-8)\) → right end up.
53401212
Analyze \(f(x)=x^4-4x^3\). a) Find the zeros and determine the end behavior. b) Find all local extrema. c) Find all inflection points and identify any stationary inflection point. d) Give a text-only graph blueprint by stating the maximal monotonicity and concavity intervals and listing the significant points in left-to-right order.

Hints

- Multiplicity at a zero can help predict whether the graph crosses with a horizontal tangent. - A critical number where \(f'\) does not change sign is not a local extremum. - Split the real line at the zeros of \(f''\) to get the concavity intervals. - Assemble the blueprint in increasing x-order rather than treating the features as unrelated facts.

Solution

1. Factoring gives \(f(x)=x^3(x-4)\). Thus \(x=0\) is a zero of multiplicity \(3\), and \(x=4\) is a simple zero. Since the leading term is \(x^4\), \(f(x)\to\infty\) as \(x\to\pm\infty\). 2. \(f'(x)=4x^2(x-3)\). The derivative is negative for \(x<3\) except for the non-sign-changing zero at \(x=0\), and positive for \(x>3\). Therefore, \((3,-27)\) is the only local extremum, a local minimum. 3. \(f''(x)=12x(x-2)\). It is positive for \(x<0\), negative for \(0<x<2\), and positive for \(x>2\). Thus the inflection points are \((0,0)\) and \((2,-16)\). Because \(f'(0)=0\), \((0,0)\) is a stationary inflection point. 4. The graph decreases and is concave up until \((0,0)\), continues decreasing and becomes concave down until \((2,-16)\), continues decreasing and becomes concave up until the minimum \((3,-27)\), then increases concave up and crosses again at \((4,0)\).

Answer

a) Zeros: \(x=0\) (multiplicity \(3\)) and \(x=4\); both ends go to \(\infty\). b) Only local extremum: local minimum \((3,-27)\). c) Inflection points \((0,0)\) and \((2,-16)\); \((0,0)\) is stationary. d) Decreasing on \(( -\infty,3)\), increasing on \((3,\infty)\); concave up on \(( -\infty,0)\) and \((2,\infty)\), concave down on \((0,2)\). Significant order: stationary inflection \((0,0)\), inflection \((2,-16)\), minimum \((3,-27)\), zero \((4,0)\).
53419512
The figure shows two functions, \(k\) and \(m\). One graph represents a function \(f\), and the other represents its derivative \(f'\). Decide which graph represents \(f\) and which represents \(f'\). Justify your answer, especially by comparing the local extrema of \(f\) with the zeros of \(f'\).
Figure for problem 534195

Hints

- Match local extrema of one graph with zeros of the other. - Compare increasing and decreasing intervals with the sign of the possible derivative. - Use the polynomial degrees as a check.

Solution

1. The blue graph \(k\) has a local maximum at \(x = -1\) and a local minimum at \(x = 3\). 2. The red graph \(m\) is zero at \(x = -1\) and \(x = 3\). It is negative on \((-1, 3)\), where \(k\) decreases, and positive outside that interval, where \(k\) increases. 3. Therefore, \(k\) represents \(f\), and \(m\) represents \(f'\).

Answer

The blue graph \(k\) represents \(f\), and the red graph \(m\) represents \(f'\). The zeros and signs of \(m\) match the local extrema and monotonicity of \(k\).
53419712
Panel a) shows three functions, \(f\), \(g\), and \(h\). Panel b) shows their derivative graphs, \(p\), \(q\), and \(r\). Match each function with its derivative and justify your choices using local extrema, zeros, or increasing and decreasing behavior. Functions: - Blue: \(f\) - Green: \(g\) - Purple: \(h\) Derivatives: - Red: \(p\) - Orange: \(q\) - Gray: \(r\)
Figure for problem 534197

Hints

- Match horizontal tangents with zeros of the derivative. - Compare increasing and decreasing intervals with the sign of the derivative. - Use symmetry and the locations of greatest slopes as additional checks.

Solution

1. The function \(f\) is a parabola with vertex at \(x = 0\). Its derivative must be a line through the origin, so \(f\) matches \(r\). 2. The function \(g\) is cubic with a local minimum at \(x = -2\) and a local maximum at \(x = 2\). Its derivative must be zero at those values and positive between them, so \(g\) matches \(p\). 3. The function \(h\) is sinusoidal. Its derivative is a cosine graph with the same period and is largest at \(x = 0\), where \(h\) has its greatest positive slope. Thus, \(h\) matches \(q\).

Answer

\(f \rightarrow r\); \(g \rightarrow p\); \(h \rightarrow q\).
53419812
The graph shows the derivative \(f'\) of a function \(f\) on \([-1, 5]\). a) On which intervals is \(f\) strictly increasing? b) At which \(x\)-values does \(f\) have local extrema? Classify each as a local maximum or local minimum. c) What can you conclude about the concavity of \(f\) at \(x = 2\)?
Figure for problem 534198

Hints

- Use the sign of \(f'\) to determine increasing intervals. - Use sign changes at zeros of \(f'\) to classify local extrema. - A local extremum of \(f'\) indicates a possible inflection point of \(f\).

Solution

1. On the displayed interval, the derivative is positive for \(-1 < x < 1\) and \(3 < x < 5\), so \(f\) is strictly increasing on \([-1, 1]\) and \([3, 5]\). 2. At \(x = 1\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. At \(x = 3\), it changes from negative to positive, so \(f\) has a local minimum. 3. The derivative graph has a local minimum at \(x = 2\). Thus, \(f''(2) = 0\) and \(f''\) changes from negative to positive. Therefore, \(f\) changes from concave down to concave up and has an inflection point at \(x = 2\).

Answer

a) \([-1, 1]\) and \([3, 5]\) b) Local maximum at \(x = 1\); local minimum at \(x = 3\) c) \(f\) has an inflection point at \(x = 2\), changing from concave down to concave up.
53421812
The figure shows a function \(f\) (solid blue) and a function \(g\) (dashed orange). One graph is the derivative of the other. a) Use local extrema and zeros to explain why \(g\) must be the derivative of \(f\), not the other way around. b) Check the relationship at \(x = 0\). Estimate the slope of \(f\) there and compare it with \(g(0)\).
Figure for problem 534218

Hints

- Match local extrema of one graph with zeros of the other. - Compare monotonicity with the sign of the possible derivative. - Read the tangent slope at \(x = 0\) and compare it with the other graph's value there.

Solution

1. The graph of \(f\) has a local maximum at \(x = -2\) and a local minimum at \(x = 2\). The graph of \(g\) is zero at those same values. Also, \(g\) is negative where \(f\) decreases and positive where \(f\) increases. Therefore, \(g = f'\). 2. The reverse assignment is impossible because \(g\) is quadratic, so its derivative would be linear, while \(f\) is cubic. 3. At \(x = 0\), the slope of \(f\) is approximately \(-1.2\). The graph of \(g\) gives \(g(0) \approx -1.2\), confirming the derivative relationship.

Answer

a) \(g = f'\). Its zeros match the local extrema of \(f\), and its sign matches where \(f\) increases or decreases. b) The slope of \(f\) at \(x = 0\) is approximately \(-1.2\), and \(g(0) \approx -1.2\).
53424812
The graphs of two polynomial functions, \(f_1\) and \(f_2\), are shown along with two derivative graphs. a) Match each function graph, (1) and (2), with its derivative graph, (A) or (B). b) Justify each match using critical points and intervals where the function is increasing or decreasing.
Figure for problem 534248

Hints

- At a smooth local maximum or minimum, the derivative is zero. - Compare where each function increases or decreases with where each derivative is positive or negative. - A quadratic function has a linear derivative, while a cubic function has a quadratic derivative.

Solution

1. Graph (1) is a downward-opening parabola with a local maximum at \(x=2\). Its derivative must be positive before \(x=2\), zero at \(x=2\), and negative after \(x=2\). Graph (B), the decreasing line \(y=-x+2\), has this sign pattern. Therefore, (1) matches (B). 2. Graph (2) is a cubic with a local maximum at \(x=-2\) and a local minimum at \(x=2\). Its derivative must be zero at \(x=-2\) and \(x=2\), positive outside those values, and negative between them. Graph (A), the upward-opening parabola \(y=0.75x^2-3\), has this sign pattern. Therefore, (2) matches (A).

Answer

a) (1) matches (B); (2) matches (A). b) The critical point of (1) at \(x=2\) matches the zero and sign change of (B). The critical points of (2) at \(x=-2\) and \(x=2\) match the zeros and sign changes of (A).
53427112
The graph shown is the graph of \(f'\), the derivative of a function \(f\). a) Find the \(x\)-coordinates of all local extrema of \(f\). Classify each as a local maximum or local minimum, and justify your answer. b) At what \(x\)-value does \(f\) have a stationary inflection point? Justify your answer using the sign behavior of \(f'\).
Figure for problem 534271

Hints

- Zeros of \(f'\) indicate points where \(f\) has a horizontal tangent. - A sign change in \(f'\) determines whether a local maximum or minimum occurs. - Consider what happens when \(f'\) equals zero but keeps the same sign on both sides. - Make sure you are interpreting the graph of the derivative, not the graph of \(f\).

Solution

1. Local extrema occur at zeros of \(f'\) where the sign changes. At \(x=-3\), \(f'\) changes from negative to positive, so \(f\) has a local minimum. At \(x=1\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. 2. At \(x=4\), \(f'(4)=0\), but \(f'\) is negative on both sides of \(x=4\). Thus, \(f\) continues decreasing and does not have a local extremum. Because \(f'\) changes from increasing to decreasing at \(x=4\), the concavity of \(f\) changes there. Therefore, \(f\) has a stationary inflection point at \(x=4\).

Answer

a) Local minimum at \(x=-3\); local maximum at \(x=1\). b) A stationary inflection point occurs at \(x=4\).
53427312
The graph shown is the graph of \(f'\), the derivative of a function \(f\). a) Does \(f\) have a local extremum at \(x=2\)? Justify your answer. b) Find the \(x\)-coordinate of the local extremum of \(f\), and classify it. c) At what \(x\)-value does \(f\) have a stationary inflection point? Justify your answer.
Figure for problem 534273

Hints

- A zero of the derivative alone does not guarantee a local extremum. - Check whether the graph of \(f'\) crosses or only touches the \(x\)-axis. - A stationary inflection point has a horizontal tangent but is not a local extremum.

Solution

1. Although \(f'(2)=0\), the derivative does not change sign at \(x=2\). Therefore, \(f\) does not have a local extremum there. 2. At \(x=-1\), \(f'\) changes from positive to negative, so \(f\) has a local maximum at \(x=-1\). 3. At \(x=2\), \(f'\) has a local maximum with value \(0\). Thus, \(f'(2)=0\) without a sign change, while \(f'\) changes from increasing to decreasing. Therefore, the concavity of \(f\) changes and \(f\) has a stationary inflection point at \(x=2\).

Answer

a) No. The derivative does not change sign at \(x=2\). b) Local maximum at \(x=-1\). c) A stationary inflection point occurs at \(x=2\).
53427512
The graph shown is the first derivative \(f'\) of a function \(f\). a) Find the x-coordinates of the inflection points of \(f\). Explain your reasoning. b) State the intervals in the displayed domain where \(f\) is concave up and concave down.
Figure for problem 534275

Hints

- The slope of \(f'\) represents \(f''\). - The x-coordinates of inflection points of \(f\) occur where \(f'\) changes from increasing to decreasing or vice versa. - Where is the graph of \(f'\) increasing? - Where is the graph of \(f'\) decreasing?

Solution

1. The graph of \(f'\) has local extrema at \(x=-2\) and \(x=2\), so \(f\) has inflection points at those x-values. 2. On the displayed domain \([-4.5,4.5]\), \(f'\) is increasing on \((-2,2)\). Therefore, \(f\) is concave up on \((-2,2)\). 3. The graph of \(f'\) is decreasing on \([-4.5,-2)\) and \((2,4.5]\). Therefore, \(f\) is concave down on those intervals.

Answer

a) \(x=-2\) and \(x=2\) b) Concave up on \((-2,2)\); concave down on \([-4.5,-2)\) and \((2,4.5]\).
53428112
The graph of the derivative \(f^{\prime}\) on \(0\le x\le6\) is shown. a) At what x-value does \(f\) have an inflection point? Justify your answer using the graph of \(f^{\prime}\). b) Given \(f(0)=0\), use geometric area to find \(f(4)\). c) Describe the graph of \(f\), incorporating the information from parts a and b.
Figure for problem 534281

Hints

- An inflection point of \(f\) occurs where \(f^{\prime}\) changes from increasing to decreasing or vice versa. - The signed area under \(f^{\prime}\) gives the change in \(f\). - Use the sign of \(f^{\prime}\) for monotonicity and its increasing or decreasing behavior for concavity.

Solution

1. The derivative \(f^{\prime}\) changes from increasing to decreasing at \(x=2\). Therefore, the concavity of \(f\) changes there, so \(f\) has an inflection point at \(x=2\). 2. By accumulation of change, \(f(4)-f(0)=\int_0^4 f^{\prime}(x)\,dx\). The region is a triangle with base \(4\) and height \(2\), so its area is \(\frac12\cdot4\cdot2=4\). Thus, \(f(4)=4\). 3. From \(x=0\) to \(x=4\), \(f^{\prime}>0\), so \(f\) increases from \((0,0)\) to a local maximum at \((4,4)\). The area from \(0\) to \(2\) is \(2\), so the inflection point is \((2,2)\). The graph is concave up on \((0,2)\), concave down on \((2,6)\), and decreases after \(x=4\).

Answer

a) \(x=2\) b) \(f(4)=4\) c) The graph passes through \((0,0)\), has an inflection point at \((2,2)\), reaches a local maximum at \((4,4)\), and then decreases. It is concave up on \((0,2)\) and concave down on \((2,6)\).
53429712
For each marked point \(A\), \(B\), and \(C\), determine whether \(f(x)\), \(f'(x)\), and \(f''(x)\) are positive, negative, or zero.
Figure for problem 534297

Hints

- Use each point’s position relative to the x-axis for the sign of \(f(x)\). - Use whether the graph is increasing, decreasing, or horizontal for the sign of \(f'(x)\). - Use concavity for the sign of \(f''(x)\). - At an inflection point, the concavity changes.

Solution

1. At \(A=(0, 0)\), the point lies on the x-axis, the graph is increasing, and it is concave down. Therefore, \(f(0)=0\), \(f'(0)>0\), and \(f''(0)<0\). 2. At \(B\), the graph has a local maximum above the x-axis and is concave down. Therefore, \(f(2)>0\), \(f'(2)=0\), and \(f''(2)<0\). 3. At \(C\), the graph is above the x-axis and decreasing. It changes concavity there. Therefore, \(f(4)>0\), \(f'(4)<0\), and \(f''(4)=0\).

Answer

Point \(A\): \(f(x)=0\), \(f'(x)>0\), \(f''(x)<0\) Point \(B\): \(f(x)>0\), \(f'(x)=0\), \(f''(x)<0\) Point \(C\): \(f(x)>0\), \(f'(x)<0\), \(f''(x)=0\)
53431912
The graphs of \(f'\) and \(f''\) are shown for a polynomial function \(f\). a) Find all x-coordinates of inflection points of \(f\) in the displayed interval. Use this example to explain the difference between a necessary condition and a sufficient condition for an inflection point. b) Find the intervals where the graph of \(f\) is concave down. c) Use the graphs to explain why \(f\) has an inflection point with locally maximum slope at \(x=1.5\).
Figure for problem 534319

Hints

- Which derivative determines the concavity of a function? - For a polynomial, a necessary condition must hold; a sufficient condition guarantees the conclusion. - How are local extrema of \(f'\) related to the slope of \(f\)? - Use the sign of \(f''\) to determine concavity.

Solution

1. Because \(f\) is a polynomial, a necessary condition for an inflection point is \(f''(x)=0\). The graph of \(f''\) has zeros at \(x=-0.5\), \(x=1.5\), and \(x=3.5\). At each zero, \(f''\) changes sign, which is sufficient for an inflection point. Therefore, all three values are x-coordinates of inflection points. 2. The graph of \(f\) is concave down where \(f''(x)<0\). In the displayed interval, this occurs on \([-1.5,-0.5)\) and \((1.5,3.5)\). 3. At \(x=1.5\), \(f''\) changes from positive to negative. Therefore, \(f'\) changes from increasing to decreasing and has a local maximum. Since \(f'\) gives the slope of \(f\), the slope of \(f\) is locally greatest there.

Answer

a) \(x=-0.5\), \(x=1.5\), and \(x=3.5\). For this polynomial, \(f''(x)=0\) is necessary, while a sign change in \(f''\) is sufficient. b) \([-1.5,-0.5)\) and \((1.5,3.5)\) c) At \(x=1.5\), \(f''\) changes from positive to negative, so \(f'\) has a local maximum and the slope of \(f\) is locally greatest.
53432212
Give three different mathematical reasons why the displayed graph cannot represent \(f(x)=x^4-4x^2+2\).
Figure for problem 534322

Hints

- Compare the equation’s symmetry with the graph. - Evaluate \(f(0)\). - Find the critical numbers from the first derivative. - Compare the required extremum at \(x=0\) with the graph.

Solution

1. The function is even, so its graph must be symmetric about the y-axis. The displayed graph is shifted to the right and lacks this symmetry. 2. The y-intercept is \(f(0)=2\), but the displayed graph crosses the y-axis at \((0,-1)\). 3. The derivative is \(f'(x)=4x(x^2-2)\), so \(x=0\) is a critical number. Since \(f''(0)=-8<0\), the graph of \(f\) must have a local maximum at \((0,2)\). The displayed graph has no extremum at \(x=0\).

Answer

The graph is incorrect because it is not symmetric about the y-axis, its y-intercept is \(-1\) instead of \(2\), and it has no local maximum at \((0, 2)\).
53433012
Let \(f(x)=x^4-2x^2\). The graph shown represents a function \(g\). Give three different reasons why the graph of \(g\) cannot be the graph of \(f'\).
Figure for problem 534330

Hints

- Determine the degree of \(f'\). - Compare the symmetry of \(f\), \(f'\), and the displayed graph. - Compare the derivative value at \(x=0\) with the graph. - Consider how the end behavior of a cubic differs from that of a parabola.

Solution

1. Differentiate: \(f'(x)=4x^3-4x\). 2. Degree: The derivative of a fourth-degree polynomial is a third-degree polynomial, but \(g\) is a parabola, so it is quadratic. 3. Symmetry: The function \(f\) is even, so \(f'\) must be odd and symmetric about the origin. The graph of \(g\) is symmetric about the y-axis. 4. Value at the origin: Since \(f'(0)=0\), the graph of \(f'\) must pass through the origin. The graph shown has \(g(0)=-2\).

Answer

Three valid reasons are: \(f'\) must be cubic, but \(g\) is quadratic; \(f'\) must be odd, but \(g\) is even; and \(f'(0)=0\), but \(g(0)=-2\).
53433512
Consider the function \(f(x)=x^4-4x^3\). The graph shown represents a function \(g\). Give three different reasons why \(g\) cannot be the graph of \(f'\).
Figure for problem 534335

Hints

- Determine the degree of \(f'\). - Factor \(f'\) and examine the multiplicity of its zero at \(x=0\). - Compare the signs of \(f'\) and \(g\) for negative \(x\)-values. - Relate the zeros of a derivative to the horizontal tangents of the original function.

Solution

1. Differentiate and factor: \(f'(x)=4x^3-12x^2=4x^2(x-3)\). 2. Degree: The derivative \(f'\) is cubic, but the graph of \(g\) is a parabola, so \(g\) is quadratic. 3. Behavior at \(x=0\): The derivative \(f'\) has a double zero at \(x=0\) and does not change sign there. The graph of \(g\) crosses the \(x\)-axis at \(x=0\), changing from positive to negative. 4. Sign for negative inputs: For \(x<0\), \(4x^2>0\) and \(x-3<0\), so \(f'(x)<0\). The displayed graph has \(g(x)>0\) for \(x<0\).

Answer

Three valid reasons are: \(f'\) must be cubic, but \(g\) is quadratic; \(f'\) has a double zero and no sign change at \(x=0\), but \(g\) changes sign there; and \(f'(x)<0\) for every \(x<0\), but the graph shows \(g(x)>0\) for \(x<0\).
53435312
The graph of the derivative \(f'\) is shown. Determine whether each statement about \(f\) is true or false, and justify your answer. 1. The graph of \(f\) is concave up on \((-1,3)\). 2. The graph of \(f\) has an inflection point at \(x=0\). 3. In the displayed interval, the graph of \(f\) is concave down for \(3<x\le5.5\).
Figure for problem 534353

Hints

- When \(f'\) is increasing, \(f\) is concave up; when \(f'\) is decreasing, \(f\) is concave down. - The x-coordinates of inflection points of \(f\) occur where \(f'\) changes from increasing to decreasing or vice versa. - Restrict your conclusions to the displayed domain.

Solution

1. True. The graph of \(f'\) is increasing on \((-1,3)\), so \(f''(x)>0\) there. Therefore, \(f\) is concave up on that interval. 2. False. An inflection point of \(f\) occurs where \(f'\) changes from increasing to decreasing or from decreasing to increasing. The graph of \(f'\) has local extrema at \(x=-1\) and \(x=3\), not at \(x=0\). 3. True. The graph of \(f'\) is decreasing for \(3<x\le5.5\), so \(f''(x)<0\) there. Therefore, \(f\) is concave down.

Answer

1. True; \(f'\) is increasing on \((-1,3)\). 2. False; \(f'\) does not have a local extremum at \(x=0\). 3. True; \(f'\) is decreasing for \(3<x\le5.5\).
53435812
A cubic polynomial \(f\) has zeros at \(x=-3\), \(x=0\), and \(x=3\), and passes through \(P=(1, -2)\). a) Find an equation for \(f\). b) Show that \(W=(0, 0)\) is an inflection point and find the tangent line there. c) Show algebraically that the graph is symmetric about the origin. Find a function \(h\) obtained by translating the graph so that its inflection point is \(W'=(2, 1)\).

Hints

- Use the zeros to write a factored cubic with an unknown leading factor. - Substitute the additional point to find the factor. - Use the second and third derivatives for the inflection point. - Test \(f(-x)\) for origin symmetry. - A shift right by \(2\) replaces \(x\) with \(x-2\), and a shift up by \(1\) adds \(1\).

Solution

1. The zeros give \(f(x)=a x(x+3)(x-3)=a(x^3-9x)\). Using \(P=(1, -2)\), \(-2=-8a\), so \(a=\frac{1}{4}\). Thus, \(f(x)=\frac{1}{4}(x^3-9x)\). 2. The derivatives are \(f'(x)=\frac{3}{4}x^2-\frac{9}{4}\), \(f''(x)=\frac{3}{2}x\), and \(f'''(x)=\frac{3}{2}\). Since \(f''(0)=0\) and \(f'''(0)\ne0\), \(W=(0, 0)\) is an inflection point. Its tangent slope is \(f'(0)=-\frac{9}{4}\), so the tangent line is \(y=-\frac{9}{4}x\). 3. Since \(f(-x)=-f(x)\), the graph is symmetric about the origin. Translating right \(2\) and up \(1\) gives \(h(x)=f(x-2)+1=\frac{1}{4}((x-2)^3-9(x-2))+1\), whose inflection point is \(W'=(2,1)\).

Answer

a) \(f(x)=\frac{1}{4}(x^3-9x)\) b) \(W=(0, 0)\); tangent line: \(y=-\frac{9}{4}x\) c) \(f(-x)=-f(x)\); \(h(x)=\frac{1}{4}((x-2)^3-9(x-2))+1\)
53437312
The graph shown is the graph of \(f'\), the derivative of a function \(f\). a) Find the \(x\)-coordinates of the local extrema of \(f\), and classify each as a local maximum or local minimum. b) Find the \(x\)-coordinate of the inflection point of \(f\). c) Use the graph of \(f'\) to explain why \(f(0)>f(-1)\).
Figure for problem 534373

Hints

- Use zeros and sign changes of \(f'\) to locate and classify local extrema of \(f\). - An inflection point of \(f\) corresponds to a local extremum of \(f'\). - Use the sign of \(f'\) on \([-1, 0]\) to compare the two function values. - Check whether the derivative graph is above or below the \(x\)-axis.

Solution

1. The zeros of \(f'\) are \(x=-4\) and \(x=2\). At \(x=-4\), \(f'\) changes from negative to positive, so \(f\) has a local minimum. At \(x=2\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. 2. An inflection point of \(f\) occurs where \(f'\) changes from increasing to decreasing. The graph of \(f'\) has its vertex at \(x=-1\), so \(f\) has an inflection point at \(x=-1\). 3. On \([-1, 0]\), the graph of \(f'\) is above the \(x\)-axis, so \(f\) is strictly increasing. Since \(0>-1\), it follows that \(f(0)>f(-1)\).

Answer

a) Local minimum at \(x=-4\); local maximum at \(x=2\). b) The inflection point occurs at \(x=-1\). c) Since \(f'(x)>0\) on \([-1, 0]\), \(f\) is strictly increasing there, so \(f(0)>f(-1)\).
53437412
The graph of the derivative \(f'\) of a polynomial function \(f\) is shown. a) Estimate the x-coordinates of the inflection points of \(f\). b) On what interval is the graph of \(f\) concave down? Justify your answer using the behavior of \(f'\). c) Explain why \(f(-1)>f(-2)\).
Figure for problem 534374

Hints

- Which special points on the derivative graph identify x-coordinates of inflection points of the original function? - What must the derivative graph do when the original function is concave down? - Is the derivative positive or negative between \(x=-2\) and \(x=-1\)? - Use the sign of \(f'\) to determine whether \(f\) is increasing or decreasing.

Solution

1. The x-coordinates of inflection points of \(f\) occur where \(f'\) has local extrema. From the graph, these occur at approximately \(x=-2.3\) and \(x=2.3\). 2. The graph of \(f\) is concave down where \(f'\) is decreasing. The derivative graph decreases between its local maximum and local minimum, so \(f\) is concave down on approximately \((-2.3,2.3)\). 3. On \([-2,-1]\), the graph of \(f'\) lies above the x-axis, so \(f'(x)>0\). Therefore, \(f\) is increasing on this interval, which gives \(f(-1)>f(-2)\).

Answer

a) Approximately \(x=-2.3\) and \(x=2.3\) b) Approximately \((-2.3,2.3)\), because \(f'\) is decreasing there. c) Since \(f'(x)>0\) on \([-2,-1]\), \(f\) is increasing and \(f(-1)>f(-2)\).
53441512
The graph of \(f'\) is shown. Determine whether each statement about \(f\) is true or false. Justify each answer. (1) \(f\) is strictly increasing on \([-3,-1]\). (2) \(f\) has a local extremum at \(x\approx0.8\). (3) \(f\) has a local minimum at \(x=-3\). (4) \(f(2)>f(-1)\).
Figure for problem 534415

Hints

- Use the sign of \(f'\) for monotonicity and extrema. - A local extremum of the derivative need not be a local extremum of the original function. - Compare \(f(2)\) and \(f(-1)\) from whether \(f\) rises or falls between those x-values.

Solution

1. True. On \((-3,-1)\), \(f'>0\), so \(f\) is strictly increasing. 2. False. Near \(x\approx0.8\), the graph of \(f'\) has a local minimum but is not zero. Thus \(f'\ne0\), so \(f\) has no local extremum there. Instead, the change from decreasing to increasing in \(f'\) gives an inflection point of \(f\). 3. True. At \(x=-3\), \(f'\) changes from negative to positive, so \(f\) has a local minimum. 4. False. Since \(f'(x)<0\) on \((-1,2)\), \(f\) is strictly decreasing there, so \(f(2)<f(-1)\).

Answer

(1) True. (2) False. (3) True. (4) False.
53442412
The graph of a function \(g\), where \(g=G^{\prime}\), is shown. Also, \(G(0)=1\). a) Approximately at what x-values does \(G\) have inflection points? Justify your answer using the graph of \(g\). b) Find an equation of the tangent line to \(G\) at \(x=0\). c) Describe the qualitative shape of \(G\) on \([-2,2]\), including its local extrema and the given point.
Figure for problem 534424

Hints

- Inflection points of \(G\) correspond to local extrema of \(G^{\prime}\). - The value \(g(0)\) is the slope of the tangent to \(G\) at \(x=0\). - Use the sign changes of \(g\) to classify the local extrema of \(G\).

Solution

1. Inflection points of \(G\) occur where \(g=G^{\prime}\) changes from increasing to decreasing or vice versa. The graph of \(g\) has local extrema at approximately \(x=-1.2\) and \(x=1.2\). Therefore, those are the approximate inflection-point x-values of \(G\). 2. The tangent slope is \(G^{\prime}(0)=g(0)=0\), and the point is \((0,1)\). Thus, the tangent line is \(y=1\). 3. The derivative \(g\) changes from negative to positive at \(x=-2\), so \(G\) has a local minimum there. It changes from positive to negative at \(x=0\), so \(G\) has a local maximum at \((0,1)\). It changes from negative to positive at \(x=2\), so \(G\) has another local minimum there. Since \(g\) is odd and \(G(0)=1\), the graph of \(G\) is symmetric about the y-axis.

Answer

a) Approximately \(x=-1.2\) and \(x=1.2\) b) \(y=1\) c) Local minima at \(x=-2\) and \(x=2\), and a local maximum at \((0,1)\); the graph is symmetric about the y-axis.
53442512
The blue graphs represent functions \(f\) and \(g\). Among the four red graphs, (1) through (4), are the derivative graphs \(f'\) and \(g'\). Match each function with its derivative graph. Justify your choices using features such as critical points, zeros, and increasing or decreasing behavior.
Figure for problem 534425

Hints

- Find where each function has a horizontal tangent. - Compare where each function increases or decreases with the sign of each possible derivative. - The derivative of a quadratic function is linear. - The derivative of a cubic function is quadratic.

Solution

1. The graph of \(f\) is an upward-opening parabola with vertex at \(x=2\). Therefore, \(f'\) must be zero at \(x=2\), negative for \(x<2\), and positive for \(x>2\). The linear graph (1) has this behavior, so \(f'\) is graph (1). 2. The graph of \(g\) has a local maximum to the left of \(x=0\) and a local minimum between \(x=3\) and \(x=4\). Its derivative must be zero at those two \(x\)-coordinates and negative between them. The upward-opening parabola (2) has this behavior, so \(g'\) is graph (2).

Answer

Graph (1) represents \(f'\), and graph (2) represents \(g'\).
53442712
The graph of \(f'\) is shown on \([-2,4]\). a) Use the zeros and vertex of the graph to find an equation for \(f'(x)\). b) Determine the open intervals in the displayed domain on which \(f\) is increasing and decreasing. c) Find the \(x\)-coordinates of all local extrema of \(f\) and classify each. d) Find the \(x\)-coordinate of the inflection point of \(f\), and state how the concavity changes there.
Figure for problem 534427

Hints

- Use the x-intercepts to write the derivative in factored form. - The sign of \(f'\) determines whether \(f\) rises or falls. - A sign change of \(f'\) classifies a local extremum of \(f\). - The slope of the derivative graph determines the concavity of \(f\).

Solution

1. The graph of \(f'\) has zeros at \(x=-1\) and \(x=3\), so write \(f'(x)=a(x+1)(x-3)\). The vertex is \((1,4)\), so \(4=a(2)(-2)\), giving \(a=-1\). Thus \(f'(x)=-x^2+2x+3\). 2. The derivative is negative on \((-2,-1)\), positive on \((-1,3)\), and negative on \((3,4)\). Therefore, \(f\) decreases on \((-2,-1)\) and \((3,4)\), and increases on \((-1,3)\). 3. At \(x=-1\), \(f'\) changes from negative to positive, so \(f\) has a local minimum. At \(x=3\), \(f'\) changes from positive to negative, so \(f\) has a local maximum. 4. Since \(f''(x)=-2x+2\), \(f''\) changes from positive to negative at \(x=1\). Thus \(f\) is concave up for \(x<1\), concave down for \(x>1\), and has an inflection point at \(x=1\).

Answer

a) \(f'(x)=-x^2+2x+3\) b) Increasing on \((-1,3)\); decreasing on \((-2,-1)\) and \((3,4)\) c) Local minimum at \(x=-1\); local maximum at \(x=3\) d) Inflection point at \(x=1\); concavity changes from up to down.
53445512
The graph of \(f'\) is shown. a) On what open intervals in the displayed domain is \(f\) increasing and decreasing? b) Find the \(x\)-coordinates of the local extrema of \(f\), and classify each. c) Use the graph's zeros and y-intercept to find an equation for \(f'(x)\). d) Find the \(x\)-coordinates of the inflection points of \(f\). Explain their relationship to the local extrema of \(f'\).
Figure for problem 534455

Hints

- Read the sign of the derivative from its position relative to the x-axis. - Use sign changes at derivative zeros to classify extrema of the original function. - Use the three zeros to write the cubic derivative in factored form. - Inflection points of \(f\) occur where the derivative switches between increasing and decreasing.

Solution

1. The derivative is negative on \((-6,-4)\) and \((1,5)\), and positive on \((-4,1)\) and \((5,7)\). Thus \(f\) decreases on \((-6,-4)\) and \((1,5)\), and increases on \((-4,1)\) and \((5,7)\). 2. At \(x=-4\), \(f'\) changes from negative to positive, so \(f\) has a local minimum. At \(x=1\), it changes from positive to negative, so \(f\) has a local maximum. At \(x=5\), it changes from negative to positive, so \(f\) has a local minimum. 3. The zeros are \(-4\), \(1\), and \(5\), so \(f'(x)=a(x+4)(x-1)(x-5)\). The graph shows \(f'(0)=2\), so \(2=20a\), giving \(a=0.1\). Hence \(f'(x)=0.1(x+4)(x-1)(x-5)\). 4. Inflection points of \(f\) occur where \(f'\) has local extrema. Differentiate: \(f''(x)=0.1(3x^2-4x-19)\). Solving \(f''(x)=0\) gives \(x=\frac{2-\sqrt{61}}{3}\) and \(x=\frac{2+\sqrt{61}}{3}\). The sign of \(f''\) changes at both values, so both are inflection-point x-coordinates.

Answer

a) Increasing on \((-4,1)\) and \((5,7)\); decreasing on \((-6,-4)\) and \((1,5)\) b) Local minima at \(x=-4\) and \(x=5\); local maximum at \(x=1\) c) \(f'(x)=0.1(x+4)(x-1)(x-5)\) d) \(x=\frac{2-\sqrt{61}}{3}\) and \(x=\frac{2+\sqrt{61}}{3}\)
53445612
The graph of \(f'\) is shown on \([-2,2]\). a) Determine whether \(f\) is increasing or decreasing on \((-2,2)\). b) Identify where \(f\) attains its absolute maximum and absolute minimum on \([-2,2]\). c) Use the zeros and y-intercept of the graph to find an equation for \(f'(x)\). d) Determine the concavity of \(f\) on \((-2,2)\) and give the \(x\)-coordinate of its inflection point.
Figure for problem 534456

Hints

- Use the sign of the derivative throughout the displayed interval. - A function that is strictly decreasing on a closed interval has its largest and smallest values at opposite endpoints. - Use the derivative graph's intercepts to determine its quadratic equation. - Concavity of \(f\) follows from whether \(f'\) is decreasing or increasing.

Solution

1. The graph of \(f'\) is below the x-axis for \(-2<x<2\), so \(f\) is strictly decreasing on \((-2,2)\). 2. Since \(f\) is continuous and strictly decreasing across the closed interval, its absolute maximum occurs at \(x=-2\) and its absolute minimum occurs at \(x=2\). 3. The zeros are \(x=-2\) and \(x=2\), so \(f'(x)=a(x-2)(x+2)\). The graph shows \(f'(0)=-2\), so \(-4a=-2\), giving \(a=\frac12\). Hence \(f'(x)=\frac12x^2-2\). 4. Since \(f''(x)=x\), \(f''<0\) on \((-2,0)\) and \(f''>0\) on \((0,2)\). Thus \(f\) is concave down on \((-2,0)\), concave up on \((0,2)\), and has an inflection point at \(x=0\).

Answer

a) \(f\) is strictly decreasing on \((-2,2)\). b) Absolute maximum at \(x=-2\); absolute minimum at \(x=2\). c) \(f'(x)=\frac12x^2-2\). d) Concave down on \((-2,0)\); concave up on \((0,2)\); inflection point at \(x=0\).
53448912
The figure shows three graphs p, q, and r from a family \(f_k\). The maximum point of each graph is marked with its exact y-value. a) Which graph represents \(h(x)=2xe^{-0.5x}\)? Justify your choice. b) Find equations for the other two graphs. c) Give the general equation for the family.
Figure for problem 534489

Hints

- Find the maximum of the given function. - Compare its exact maximum height with the marked graph maxima. - A multiplier outside the function creates a vertical scale.

Solution

1. The derivative of \(h\) is \(h'(x)=(2-x)e^{-0.5x}\). It changes from positive to negative at \(x=2\), so the maximum occurs there. Its value is \(h(2)=\frac{4}{e}\), which matches graph q. 2. All three graphs have the same zero and maximum x-coordinate, so they differ by a vertical scale factor. Their marked maximum heights are \(\frac{2}{e}\), \(\frac{4}{e}\), and \(\frac{6}{e}\). 3. Graph p has half the height of q, so its equation is \(xe^{-0.5x}\). Graph r has \(1.5\) times the height of q, so its equation is \(3xe^{-0.5x}\). 4. The family is \(f_k(x)=kxe^{-0.5x}\), where \(k>0\).

Answer

a) Graph q b) p: \(xe^{-0.5x}\); r: \(3xe^{-0.5x}\) c) \(f_k(x)=kxe^{-0.5x}\), \(k>0\)
53449512
The graph of the derivative \(f^{\prime}\) of a periodic function \(f\) is shown. a) Find all x-values in \([0,6]\) where \(f\) has a local extremum, and classify each. b) Where is \(f\) strictly decreasing on the displayed interval? c) Find all inflection-point x-values of \(f\) in \([0,6]\). d) Find an equation for \(f^{\prime}\) in the form \(f^{\prime}(x)=a\cos(bx)\).
Figure for problem 534495

Hints

- Use zeros and sign changes of \(f^{\prime}\) to classify local extrema of \(f\). - The function decreases where its derivative is negative. - Local extrema of \(f^{\prime}\) correspond to inflection points of \(f\). - Use amplitude and period to determine the cosine parameters.

Solution

1. The derivative is \(0\) at \(x=1.5\) and \(x=4.5\). It changes from positive to negative at \(x=1.5\), so \(f\) has a local maximum there. It changes from negative to positive at \(x=4.5\), so \(f\) has a local minimum there. 2. The function \(f\) is strictly decreasing where \(f^{\prime}<0\), which is \((1.5,4.5)\). 3. Inflection points of \(f\) occur where \(f^{\prime}\) changes from increasing to decreasing or vice versa. The periodic derivative has extrema at \(x=0\), \(x=3\), and \(x=6\), so these are the requested x-values. 4. The amplitude is \(2\), and the period is \(6\). Thus, \(a=2\) and \(b=\frac{2\pi}{6}=\frac{\pi}{3}\). Therefore, \(f^{\prime}(x)=2\cos(\frac{\pi}{3}x)\).

Answer

a) Local maximum at \(x=1.5\); local minimum at \(x=4.5\) b) \((1.5,4.5)\) c) \(x=0\), \(x=3\), and \(x=6\) d) \(f^{\prime}(x)=2\cos(\frac{\pi}{3}x)\)
53452112
The graph of \(f'\) is shown. Determine whether each statement about \(f\) is true or false. Justify each answer. (1) \(f\) has a local minimum at \(x=0\). (2) \(f\) is strictly decreasing on \((0,3)\). (3) \(f\) has an inflection point at \(x=0\). (4) \(f\) has local maxima at \(x=-3\) and \(x=3\).
Figure for problem 534521

Hints

- Use the sign of \(f'\) to determine whether \(f\) rises or falls. - A zero of \(f'\) gives an extremum only when the derivative changes sign. - For inflection points, track whether \(f'\) itself is increasing or decreasing.

Solution

1. Statement (1) is true. At \(x=0\), \(f'\) changes from negative to positive, so \(f\) has a local minimum. 2. Statement (2) is false. On \((0,3)\), \(f'>0\), so \(f\) is strictly increasing. 3. Statement (3) is false. An inflection point of \(f\) occurs where \(f'\) changes from increasing to decreasing or vice versa. At \(x=0\), \(f'\) is increasing through a zero, so the concavity of \(f\) does not change there. 4. Statement (4) is true. At both \(x=-3\) and \(x=3\), \(f'\) changes from positive to negative, so \(f\) has a local maximum.

Answer

(1) True (2) False (3) False (4) True
53452212
The function \(f(x)=\frac{4}{x^2+2}\) is represented by one of the four graphs shown. a) Which graph represents \(f\)? Justify your choice using characteristic features. b) Without differentiating, determine the number and location of the zeros of \(f'\). Use the graph of \(f\). c) Describe the symmetry of \(f\), and use it to predict the symmetry of \(f'\). d) Differentiate \(f\) to confirm your prediction. Then state the sign of \(f'\) on each side of its zero and give the horizontal asymptote of \(f'\).
Figure for problem 534522

Hints

- Compare the y-intercept, sign, and end behavior of the formula with the four graphs. - Horizontal tangents of \(f\) correspond to zeros of \(f'\). - Think about how differentiating an even graph affects symmetry. - Use the derivative formula only after making the graphical prediction.

Solution

1. Since \(f(0)=2\), \(f(x)>0\), and \(f(x)\to0\) as \(x\to\pm\infty\), graph (1) represents \(f\). 2. Zeros of \(f'\) occur where \(f\) has horizontal tangents. Graph (1) has exactly one horizontal tangent, at its maximum \(x=0\). Thus \(f'\) has exactly one zero at \(x=0\). 3. The function \(f\) is even, so its derivative \(f'\) is odd. 4. Differentiating gives \(f'(x)=-\frac{8x}{(x^2+2)^2}\). Thus \(f'(x)>0\) for \(x<0\), \(f'(0)=0\), and \(f'(x)<0\) for \(x>0\). Also \(f'(x)\to0\) as \(x\to\pm\infty\), so its horizontal asymptote is \(y=0\).

Answer

a) Graph (1) b) One zero: \(x=0\) c) \(f\) is even; \(f'\) is odd. d) \(f'(x)=-\frac{8x}{(x^2+2)^2}\); \(f'>0\) for \(x<0\), \(f'<0\) for \(x>0\); horizontal asymptote \(y=0\).
53453612
The graph of \(f'(x)=(x-1)e^{-x/2}\) is shown. a) Find the x-value where \(f\) has a local extremum. Classify it and justify your answer. b) Determine where \(f\) is concave up and concave down. Give the x-coordinate of the inflection point. c) Describe what happens to the slope of \(f\) as \(x\to\infty\). Explain why this fact alone does not determine whether \(f\) has a horizontal asymptote.
Figure for problem 534536

Hints

- Classify an extremum from the sign change of the first derivative. - Concavity depends on whether the derivative is increasing or decreasing. - A limiting slope describes steepness, not the actual height of the graph.

Solution

1. At \(x=1\), \(f'\) changes from negative to positive, so \(f\) has a local minimum there. 2. Differentiate the given derivative: \(f''(x)=\frac{3-x}{2}e^{-x/2}\). Since the exponential factor is positive, \(f''>0\) for \(x<3\) and \(f''<0\) for \(x>3\). Thus \(f\) is concave up for \(x<3\), concave down for \(x>3\), and has an inflection point at \(x=3\). 3. As \(x\to\infty\), \(f'(x)\to0\), so the graph of \(f\) becomes nearly horizontal. A slope approaching \(0\) does not by itself determine the function values, so it does not by itself prove that \(f\) approaches a horizontal asymptote.

Answer

a) Local minimum at \(x=1\) b) Concave up for \(x<3\); concave down for \(x>3\); inflection point at \(x=3\) c) \(f'(x)\to0\), so the graph becomes nearly horizontal; this alone does not prove a horizontal asymptote.
53454312
The graphs of functions \(f\) and \(g\) are shown. One function is the derivative of the other. a) Explain why \(g=f^{\prime}\). Use extrema and intervals of increase or decrease in your explanation. b) Estimate the interval on which the graph of \(f\) is concave down. c) Describe the general shape of \(f^{\prime\prime}\). Identify the important features of the graph of \(g\) that determine your description.
Figure for problem 534543

Hints

- Compare zeros of a possible derivative with extrema of the original function. - The sign of a derivative must agree with where the original function increases or decreases. - Because \(f^{\prime\prime}=g^{\prime}\), determine where \(g\) rises, falls, and has horizontal tangents. - Changes in the concavity of \(g\) help locate extrema of \(g^{\prime}\).

Solution

1. The graph of \(f\) has a local maximum at \(x=0\), and \(g\) has a zero there with a sign change from positive to negative. Also, \(f\) increases where \(g>0\) and decreases where \(g<0\). Therefore, \(g=f^{\prime}\). 2. The graph of \(f\) is concave down where \(f^{\prime\prime}(x)<0\). Since \(f^{\prime\prime}=g^{\prime}\), this occurs where \(g\) is decreasing, approximately on \((-0.6, 0.6)\). 3. The graph of \(f^{\prime\prime}\) has zeros near \(x=-0.6\) and \(x=0.6\), where \(g\) has local extrema. It is negative between these zeros and positive outside them in the displayed domain. 4. The steepest downward slope of \(g\) occurs at \(x=0\), so \(f^{\prime\prime}\) has a local minimum there. The changes in concavity of \(g\) near \(x=-1\) and \(x=1\) produce local maxima of \(f^{\prime\prime}\) near those x-values.

Answer

a) \(g=f^{\prime}\) because the zero and sign of \(g\) agree with the local maximum and monotonicity of \(f\). b) Approximately \((-0.6, 0.6)\) c) The graph of \(f^{\prime\prime}\) is positive outside approximately \((-0.6, 0.6)\), negative inside, has zeros near \(x=\pm0.6\), a local minimum at \(x=0\), and local maxima near \(x=\pm1\).
53456012
The graph of the derivative \(f^{\prime}\) of a continuous function \(f\) is shown. a) Find the intervals where \(f\) is strictly increasing and strictly decreasing. b) Find all local-extremum x-values of \(f\), and classify each. c) Where is \(f\) concave up? At what x-value does \(f\) have an inflection point? d) Given \(f(0)=4\), decide whether \(f(5)\) is greater than or less than \(4\). Justify your answer using the graph of \(f^{\prime}\).
Figure for problem 534560

Hints

- The sign of \(f^{\prime}\) determines monotonicity. - Sign changes of \(f^{\prime}\) classify local extrema. - The increasing or decreasing behavior of \(f^{\prime}\) determines concavity. - Signed area under \(f^{\prime}\) gives the change in \(f\).

Solution

1. The derivative is positive on \((-4,-2)\) and \((4,6)\), so \(f\) is increasing there. It is negative on \((-2,4)\), so \(f\) is decreasing there. 2. At \(x=-2\), \(f^{\prime}\) changes from positive to negative, so \(f\) has a local maximum. At \(x=4\), it changes from negative to positive, so \(f\) has a local minimum. 3. The function \(f\) is concave up where \(f^{\prime}\) is increasing. The derivative has its minimum at \(x=1\) and increases for \(x>1\), so \(f\) is concave up on \((1,6)\) in the displayed interval. The inflection-point x-value is \(x=1\). 4. The change is \(f(5)-f(0)=\int_0^5 f^{\prime}(x)\,dx\). The negative signed area from \(0\) to \(4\) has greater magnitude than the positive area from \(4\) to \(5\), so the net change is negative. Therefore, \(f(5)<4\).

Answer

a) Increasing on \((-4,-2)\) and \((4,6)\); decreasing on \((-2,4)\) b) Local maximum at \(x=-2\); local minimum at \(x=4\) c) Concave up on \((1,6)\); inflection point at \(x=1\) d) \(f(5)<4\)
53456212
The graph shown is \(f'\), the derivative of a cubic polynomial \(f\). Give a text-only graph blueprint for \(f\). a) Find the x-coordinates of all local extrema of \(f\) and classify them. b) State the maximal intervals on which \(f\) is increasing and decreasing. c) State the maximal intervals on which \(f\) is concave up and concave down, and give the inflection-point x-coordinate. d) List the significant x-values from left to right and describe the resulting sequence of graph features.
Figure for problem 534562

Hints

- First use the zeros and sign of \(f'\) to organize the monotonicity and extrema. - The original function is concave up where its derivative graph is increasing and concave down where the derivative graph is decreasing. - The vertex of the derivative graph supplies the inflection input of the cubic. - Put the three significant x-values in order before writing the final blueprint.

Solution

1. The zeros of \(f'\) are \(x=-1\) and \(x=3\). The derivative is positive for \(x<-1\), negative for \(-1<x<3\), and positive for \(x>3\). Hence \(f\) has a local maximum at \(x=-1\) and a local minimum at \(x=3\). 2. The same sign chart gives increasing intervals \(( -\infty,-1)\) and \((3,\infty)\), with decreasing interval \((-1,3)\). 3. The graph of \(f'\) decreases until its vertex at \(x=1\) and increases afterward. Thus \(f''<0\) for \(x<1\) and \(f''>0\) for \(x>1\). Therefore, \(f\) is concave down on \(( -\infty,1)\), concave up on \((1,\infty)\), and has an inflection point at \(x=1\). 4. Left to right, the graph increases concave down to a local maximum at \(x=-1\), decreases concave down to the inflection input \(x=1\), continues decreasing concave up to a local minimum at \(x=3\), then increases concave up.

Answer

a) Local maximum at \(x=-1\); local minimum at \(x=3\). b) Increasing on \(( -\infty,-1)\) and \((3,\infty)\); decreasing on \((-1,3)\). c) Concave down on \(( -\infty,1)\); concave up on \((1,\infty)\); inflection-point x-coordinate \(1\). d) Left-to-right features: maximum at \(-1\), inflection at \(1\), minimum at \(3\), with the monotonicity/concavity sequence stated above.
53458812
Match each displayed graph with one of the following functions. Use each function's derivative together with intercepts, symmetry, and end behavior to justify each match. \(f_1(x)=e^x-2\) \(f_2(x)=2e^{-x}\) \(f_3(x)=4e^{-0.2x^2}\) \(f_4(x)=(x-1)e^x\)
Figure for problem 534588

Hints

- Evaluate each function at \(x=0\) and find any zeros. - Differentiate each function and use the sign of the derivative to determine monotonicity and extrema. - Compare horizontal asymptotes and end behavior. - Check for symmetry about the y-axis.

Solution

1. For \(f_1(x)=e^x-2\), the y-intercept is \(-1\), the horizontal asymptote is \(y=-2\) as \(x\to-\infty\), and \(f_1'(x)=e^x>0\), so the function is strictly increasing. These features match graph a). 2. For \(f_2(x)=2e^{-x}\), the y-intercept is \(2\), \(f_2(x)\to0\) as \(x\to\infty\), and \(f_2'(x)=-2e^{-x}<0\), so the function is strictly decreasing. These features match graph b). 3. For \(f_3(x)=4e^{-0.2x^2}\), the function is even, and \(f_3'(x)=-1.6xe^{-0.2x^2}\). Thus, it increases for \(x<0\), decreases for \(x>0\), and has a maximum value of \(4\) at \(x=0\). These features match graph c). 4. For \(f_4(x)=(x-1)e^x\), the zero is \(x=1\), the y-intercept is \(-1\), and \(f_4'(x)=xe^x\). Thus, it decreases for \(x<0\), increases for \(x>0\), and has a local minimum at \(x=0\). These features match graph d).

Answer

a) \(f_1\); b) \(f_2\); c) \(f_3\); d) \(f_4\)
53465412
The graph of \(f(x)=x^3-6x^2+9x\) is shown on \([-1,5]\). a) Find the critical numbers of \(f\). b) Give the open intervals in the displayed domain on which \(f\) is increasing and decreasing. c) Find an equation for \(f'(x)\), and determine where \(f'(x)\ge0\) on the displayed domain. d) At what x-value does \(f'\) attain its minimum? Explain the connection to the graph of \(f\). e) Determine the signs of \(f'(0)\) and \(f'(2)\).
Figure for problem 534654

Hints

- Differentiate and factor before making the sign chart. - Use the derivative's sign to determine monotonicity. - The minimum of the derivative corresponds to the point where its slope changes from negative to positive. - Compare the requested derivative values with zero rather than relying only on the graph.

Solution

1. Differentiate: \(f'(x)=3x^2-12x+9=3(x-1)(x-3)\). Thus the critical numbers are \(x=1\) and \(x=3\). 2. The derivative is positive on \((-1,1)\) and \((3,5)\), and negative on \((1,3)\). Therefore, \(f\) increases on \((-1,1)\) and \((3,5)\), and decreases on \((1,3)\). 3. On the displayed domain, \(f'(x)\ge0\) for \(x\in[-1,1]\cup[3,5]\). 4. The quadratic \(f'\) has its vertex midway between its zeros, at \(x=2\). This is where the slope of \(f\) is smallest and where \(f''\) changes sign, so \(x=2\) is the inflection-point x-coordinate of \(f\). 5. \(f'(0)=9>0\), while \(f'(2)=-3<0\).

Answer

a) \(x=1\) and \(x=3\) b) Increasing on \((-1,1)\) and \((3,5)\); decreasing on \((1,3)\) c) \(f'(x)=3(x-1)(x-3)\); \(f'(x)\ge0\) on \([-1,1]\cup[3,5]\) d) \(x=2\); it is the inflection-point x-coordinate of \(f\). e) \(f'(0)>0\) and \(f'(2)<0\)
53471512
The graph of \(f'\) is shown. a) Find every x-value where \(f\) has a local minimum. Justify your answer. b) At approximately what x-values does \(f\) have inflection points? c) Determine whether the following statement is true or false: “\(f\) is strictly increasing for every displayed \(x>3\).” Justify your answer.
Figure for problem 534715

Hints

- A negative-to-positive sign change of the derivative gives a local minimum. - Inflection points of \(f\) correspond to local extrema of \(f'\). - Read increasing behavior of \(f\) from where \(f'\) is positive.

Solution

1. A local minimum of \(f\) occurs where \(f'\) changes from negative to positive. The graph shows this at \(x=-4\) and \(x=3\). 2. Inflection points of \(f\) occur where \(f'\) has local extrema. From the graph, these x-values are approximately \(x=-2.7\) and \(x=1.4\). 3. The statement is true. For every displayed \(x>3\), the graph of \(f'\) is above the x-axis, so \(f'(x)>0\) and \(f\) is strictly increasing there.

Answer

a) \(x=-4\) and \(x=3\) b) Approximately \(x=-2.7\) and \(x=1.4\) c) True; \(f'(x)>0\) for every displayed \(x>3\).
53483812
Graphs 1, 2, and 3 represent a function \(f\), its first derivative \(f'\), and its second derivative \(f''\). Identify each graph and justify your matches by comparing zeros, local extrema, and increasing/decreasing behavior.
Figure for problem 534838

Hints

- Zeros of a derivative correspond to horizontal tangents of the function one level above it. - Compare derivative signs with increasing and decreasing intervals. - Build the derivative chain one link at a time.

Solution

1. Graph 3 has a local minimum at \(x=0\). Graph 1 is zero there and changes from negative to positive, so Graph 1 is the derivative of Graph 3. 2. Graph 1 has local extrema at \(x=-1\) and \(x=1\). Graph 2 is zero at those x-values, and its sign matches where Graph 1 increases or decreases. Therefore, Graph 2 is the derivative of Graph 1. 3. Thus Graph 3 is \(f\), Graph 1 is \(f'\), and Graph 2 is \(f''\).

Answer

Graph 1: \(f'\); Graph 2: \(f''\); Graph 3: \(f\)
53485312
The graph shown belongs to a polynomial function \(f\). 1. Determine the least possible degree of \(f\). Justify your answer from the graph. 2. Use the graph's symmetry to write a general form for \(f\). 3. Use the marked points to find an equation for \(f\).
Figure for problem 534853

Hints

- Count the graph's turning points and relate that number to polynomial degree. - Decide whether the graph has y-axis symmetry or \(180^\circ\) rotational symmetry about the origin. - For origin symmetry, keep only odd powers in the cubic form. - Use both the coordinates and the horizontal tangent at the marked local maximum.

Solution

1. The graph has two local extrema. A polynomial of degree \(n\) has at most \(n-1\) turning points, so its degree is at least \(3\). A cubic is therefore the least possible degree. 2. The graph has \(180^\circ\) rotational symmetry about the origin, so \(f\) is odd. For a cubic, \(f(x)=ax^3+cx\). 3. The marked local maximum is \((-1, 2)\). Therefore, \(f(-1)=2\) and \(f'(-1)=0\). These conditions give \(-a-c=2\) and \(3a+c=0\). Solving the system gives \(a=1\) and \(c=-3\). Thus, \(f(x)=x^3-3x\).

Answer

1. Least possible degree: \(3\) 2. \(f(x)=ax^3+cx\) 3. \(f(x)=x^3-3x\)
53485512
Consider the graph of a polynomial function \(f\). 1. Explain why the degree of \(f\) must be at least \(4\). 2. Describe the graph's symmetry and write a corresponding general form for \(f\). 3. Use the marked extrema to find an equation for \(f\).
Figure for problem 534855

Hints

- Count the graph's turning points and relate that number to polynomial degree. - Compare the left and right halves of the graph to identify its symmetry. - Determine which powers can appear in a polynomial that is symmetric about the y-axis. - Use both the coordinates and the horizontal tangent at one marked extremum.

Solution

1. The graph has three local extrema. A polynomial of degree \(n\) has at most \(n-1\) turning points, so the degree must be at least \(4\). 2. The graph is symmetric about the y-axis, so \(f\) is even. For a fourth-degree polynomial, write \(f(x)=ax^4+bx^2+c\). 3. The marked local maximum \((0, 0)\) gives \(c=0\), so \(f(x)=ax^4+bx^2\). The local minimum \((2, -4)\) gives \(16a+4b=-4\). Because the tangent there is horizontal, \(f'(2)=0\). Since \(f'(x)=4ax^3+2bx\), this gives \(32a+4b=0\). Solving the system yields \(a=\frac{1}{4}\) and \(b=-2\). Therefore, \(f(x)=\frac{1}{4}x^4-2x^2\).

Answer

1. The degree is at least \(4\) because the graph has three turning points. 2. The graph is symmetric about the y-axis, so \(f(x)=ax^4+bx^2+c\). 3. \(f(x)=\frac{1}{4}x^4-2x^2\)
53485712
The graph of \(f\) is a fourth-degree polynomial that is symmetric about the y-axis. 1. Write a general form for \(f\) that uses the symmetry. 2. Find an equation for \(f\). The graph has a local maximum at \(M=(0, 4)\), and its inflection points lie on the x-axis at \(x=-1\) and \(x=1\).

Hints

- Symmetry about the y-axis restricts the powers that may appear. - An inflection point on the x-axis gives a function-value condition and a second-derivative condition. - Use the y-intercept to determine the constant term. - Solve the resulting two-equation system for the remaining coefficients.

Solution

1. Because \(f\) is even, write \(f(x)=ax^4+bx^2+c\). 2. The point \(M=(0, 4)\) gives \(c=4\). At the inflection point with \(x=1\), both \(f(1)=0\) and \(f''(1)=0\). The first condition gives \(a+b=-4\). Since \(f''(x)=12ax^2+2b\), the second gives \(12a+2b=0\), or \(6a+b=0\). Solving the system yields \(a=\frac{4}{5}\) and \(b=-\frac{24}{5}\). Therefore, \(f(x)=\frac{4}{5}x^4-\frac{24}{5}x^2+4\). 3. Since \(f''(0)=-\frac{48}{5}<0\), \(M=(0, 4)\) is a local maximum. Also, \(f'''(\pm1)=\pm\frac{96}{5}\ne0\), so \(x=-1\) and \(x=1\) are indeed inflection-point x-coordinates.

Answer

1. \(f(x)=ax^4+bx^2+c\) 2. \(f(x)=\frac{4}{5}x^4-\frac{24}{5}x^2+4\)
53485812
The graph shown belongs to a fourth-degree polynomial \(g\) that is symmetric about the y-axis. 1. Use the marked points to find an equation for \(g\). 2. Find the exact coordinates of the local maxima.
Figure for problem 534858

Hints

- Use the y-axis symmetry to reduce the number of coefficients. - A marked inflection point gives conditions on the function and its second derivative. - Find the critical numbers from the first derivative, then classify the extrema. - Keep \(\sqrt{3}\) as an exact value.

Solution

1. Because \(g\) is even, write \(g(x)=ax^4+bx^2+c\). The graph passes through the origin, so \(c=0\). The marked inflection point \(I_2=\left(1, \frac{5}{2}\right)\) gives \(g(1)=\frac{5}{2}\) and \(g''(1)=0\). Therefore, \(a+b=\frac{5}{2}\) and \(12a+2b=0\). Solving gives \(a=-\frac{1}{2}\) and \(b=3\), so \(g(x)=-\frac{1}{2}x^4+3x^2\). Since \(g'''(\pm1)=\mp12\ne0\), both marked points are indeed inflection points. 2. The derivative is \(g'(x)=-2x^3+6x=-2x(x^2-3)\). Thus, the critical numbers are \(x=0\) and \(x=\pm\sqrt{3}\). Since \(g''(0)=6>0\), \(x=0\) is a local minimum. At \(x=\pm\sqrt{3}\), \(g''(x)=-6x^2+6=-12<0\), so both are local maxima. Their common function value is \(g(\pm\sqrt{3})=-\frac{1}{2}(9)+3(3)=\frac{9}{2}\).

Answer

1. \(g(x)=-\frac{1}{2}x^4+3x^2\) 2. Local maxima: \((-\sqrt{3}, \frac{9}{2})\) and \((\sqrt{3}, \frac{9}{2})\)
53489912
A bridge arch is modeled by a fourth-degree polynomial that is symmetric about the y-axis. The bridge spans \(40\,\text{ft}\), and the arch reaches a maximum height of \(20\,\text{ft}\) at its center. At the ends of the span, \(x=-20\) and \(x=20\), the arch meets the ground with horizontal tangent lines. Find an equation for the arch when the origin is at the center of the span on ground level.

Hints

- Use the y-axis symmetry to simplify the polynomial form. - Translate “meets the ground with a horizontal tangent” into a function-value condition and a derivative condition. - Use the center height to determine the constant term. - Solve the resulting system for the remaining coefficients.

Solution

1. Because the arch is symmetric about the y-axis, write \(f(x)=ax^4+bx^2+c\). 2. The center point \((0, 20)\) gives \(c=20\). 3. The endpoint \((20, 0)\) gives \(160{,}000a+400b+20=0\). 4. A horizontal tangent at \(x=20\) requires \(f'(20)=0\). Since \(f'(x)=4ax^3+2bx\), \(32{,}000a+40b=0\), so \(b=-800a\). 5. Substitution into the endpoint equation gives \(-160{,}000a=-20\), so \(a=\frac{1}{8000}\) and \(b=-\frac{1}{10}\). 6. Therefore, \(f(x)=\frac{1}{8000}x^4-\frac{1}{10}x^2+20\), for \(-20\le x\le20\). Also, \(f''(0)=-\frac{1}{5}<0\), confirming the maximum at the center.

Answer

\(f(x)=\frac{1}{8000}x^4-\frac{1}{10}x^2+20\), for \(-20\le x\le20\)
55033312
A differentiable function \(h\) has the piecewise-linear derivative shown on \([-5,5]\). Use the graph of \(h'\) to give all of the following for \(h\): a) maximal open intervals of increase and decrease; b) x-coordinates and classifications of all local extrema; c) maximal open intervals of concavity; d) x-coordinates of all inflection points.
Figure for problem 550333

Hints

- Use the derivative's sign for one set of features and the derivative's rise or fall for another. - Treat zeros of the derivative and turning points of the derivative graph as different kinds of information. - Work through monotonicity and concavity separately before combining the conclusions.

Solution

1. The derivative is positive on \((-5,-3)\) and \((1,5)\), and negative on \((-3,1)\). Thus \(h\) increases on \((-5,-3)\) and \((1,5)\), and decreases on \((-3,1)\). 2. At \(x=-3\), \(h'\) changes from positive to negative, so \(h\) has a local maximum. At \(x=1\), it changes from negative to positive, so \(h\) has a local minimum. 3. The graph of \(h'\) decreases on \((-5,-1)\), increases on \((-1,3)\), and decreases on \((3,5)\). Therefore, \(h\) is concave down on \((-5,-1)\) and \((3,5)\), and concave up on \((-1,3)\). 4. Concavity changes at \(x=-1\) and \(x=3\), so these are inflection-point x-coordinates.

Answer

a) Increasing on \((-5,-3)\) and \((1,5)\); decreasing on \((-3,1)\). b) Local maximum at \(x=-3\); local minimum at \(x=1\). c) Concave down on \((-5,-1)\) and \((3,5)\); concave up on \((-1,3)\). d) Inflection-point x-coordinates: \(x=-1\) and \(x=3\).
55033412
The table gives values of \(p'\). Assume \(p'\) is linear between consecutive listed x-values. <table> <tr><th>\(x\)</th><th>\(p'(x)\)</th></tr> <tr><td>\(-4\)</td><td>\(3\)</td></tr> <tr><td>\(-2\)</td><td>\(0\)</td></tr> <tr><td>\(0\)</td><td>\(-2\)</td></tr> <tr><td>\(2\)</td><td>\(0\)</td></tr> <tr><td>\(4\)</td><td>\(4\)</td></tr> </table> a) Give the maximal open intervals on which \(p\) is increasing and decreasing. b) Classify the critical numbers \(x=-2\) and \(x=2\). c) On which maximal open intervals is \(p\) concave up or concave down?

Hints

- Use the sign of the derivative to determine how the original function moves. - At a zero of the derivative, compare the signs on the two sides before classifying it. - For concavity, look for where the derivative values trend downward or upward.

Solution

1. Because \(p'\) is positive on \((-4,-2)\), negative on \((-2,2)\), and positive on \((2,4)\), \(p\) increases on \((-4,-2)\) and \((2,4)\), and decreases on \((-2,2)\). 2. At \(x=-2\), \(p'\) changes from positive to negative, so \(p\) has a local maximum. At \(x=2\), it changes from negative to positive, so \(p\) has a local minimum. 3. The listed values of \(p'\) decrease from \(x=-4\) to \(x=0\), then increase from \(x=0\) to \(x=4\). Therefore, \(p\) is concave down on \((-4,0)\) and concave up on \((0,4)\).

Answer

a) Increasing on \((-4,-2)\) and \((2,4)\); decreasing on \((-2,2)\). b) Local maximum at \(x=-2\); local minimum at \(x=2\). c) Concave down on \((-4,0)\); concave up on \((0,4)\).
55616612
Give an exact **graph blueprint** for a differentiable function \(f\). You are given \(f'(x)=-(x+1)^2(x-2)\), together with \(f(-1)=0\), \(f(1)=4\), and \(f(2)=\tfrac{27}{4}\). a) Classify the horizontal tangencies at \(x=-1\) and \(x=2\) from the sign of \(f'\). b) Differentiate \(f'\) to find every inflection-point x-coordinate. c) Give the complete left-to-right monotonicity/concavity blueprint and name each supplied landmark with coordinates.

Hints

- A squared factor in \(f'\) gives a zero where the sign of \(f'\) may stay the same. - Differentiate the supplied expression for \(f'\) to get \(f''\); do not integrate. - Split the blueprint at every x-value where either monotonicity or concavity changes.

Solution

1. Since \(f'(x)=-(x+1)^2(x-2)\), the squared factor does not change sign at \(x=-1\). Thus \(f'>0\) on both sides of \(-1\). At \(x=2\), \(f'\) changes from positive to negative. 2. Therefore \((-1,0)\) is not a local extremum, while \((2,\tfrac{27}{4})\) is a local maximum. 3. Differentiate the given derivative: \(f''(x)=-3x^2+3=3(1-x^2)\). Hence \(f''=0\) at \(x=-1\) and \(x=1\), and its sign changes at both values. 4. At \(x=-1\), the horizontal tangent together with the concavity change makes \((-1,0)\) a stationary inflection point. At \(x=1\), \((1,4)\) is a nonstationary inflection point. 5. The graph is increasing/concave down on \(( -\infty,-1)\), increasing/concave up on \((-1,1)\), increasing/concave down on \((1,2)\), and decreasing/concave down on \((2,\infty)\).

Answer

Stationary inflection \((-1,0)\); nonstationary inflection \((1,4)\); local maximum \((2,\tfrac{27}{4})\). Blueprint: ↑/concave down on \(( -\infty,-1)\), ↑/concave up on \((-1,1)\), ↑/concave down on \((1,2)\), and ↓/concave down on \((2,\infty)\).
55616712
On the closed interval \([-4,4]\), give an exact **graph blueprint** for \(f\). The derivative signs are: \(f'(x)>0\) on \((-4,-1)\), \(f'(-1)=0\), \(f'(x)<0\) on \((-1,2)\), \(f'(2)=0\), and \(f'(x)>0\) on \((2,4)\). Also, \(f''(x)<0\) on \((-4,0)\) and \(f''(x)>0\) on \((0,4)\). Function values are \(f(-4)=0\), \(f(-1)=5\), \(f(0)=3\), \(f(2)=1\), and \(f(4)=4\). Give the segment-by-segment blueprint, classify the two interior extrema and the inflection point, and identify the absolute maximum and minimum on \([-4,4]\).

Hints

- Use all breakpoints where either derivative sign changes. - Endpoint values matter for absolute extrema even though endpoints are not interior critical numbers. - Keep local classification and absolute comparison as separate steps.

Solution

1. \((-4,-1)\): increasing and concave down. 2. At \((-1,5)\), \(f'\) changes positive to negative, so there is a local maximum. 3. \((-1,0)\): decreasing and concave down. 4. At \((0,3)\), concavity changes down to up, so this is an inflection point. 5. \((0,2)\): decreasing and concave up. 6. At \((2,1)\), \(f'\) changes negative to positive, so there is a local minimum. 7. \((2,4)\): increasing and concave up. 8. Compare the supplied candidate values at the endpoints and local extrema: \(0,5,1,4\). The absolute maximum is \(5\) at \(x=-1\); the absolute minimum is \(0\) at the endpoint \(x=-4\).

Answer

Blueprint: ↑/concave down on \((-4,-1)\); local max \((-1,5)\); ↓/concave down to inflection \((0,3)\); ↓/concave up to local min \((2,1)\); ↑/concave up on \((2,4)\). Absolute max \(5\) at \(x=-1\); absolute min \(0\) at \(x=-4\).
52953212
Consider \(f(x)=\sqrt{4x^2+4x+10}\). 1. Find the location and type of the extremum. 2. The second derivative is \(f^{\prime\prime}(x)=\frac{36}{(4x^2+4x+10)^{3/2}}\). Explain why \(f\) has no inflection points. 3. Find \(\lim_{x\to\infty}f^{\prime}(x)\) and \(\lim_{x\to-\infty}f^{\prime}(x)\). 4. Use the end behavior to find the two slant asymptotes of the graph.

Hints

- Use the sign of the given second derivative to classify the critical point. - Remember that \(\sqrt{x^2}=|x|\) when evaluating limits at infinity. - Complete the square inside the radical to identify the intercepts of the slant asymptotes.

Solution

1. The first derivative is \(f^{\prime}(x)=\frac{4x+2}{\sqrt{4x^2+4x+10}}\). Setting the numerator equal to zero gives \(x=-\frac{1}{2}\). Since \(f(-\frac{1}{2})=3\) and \(f^{\prime\prime}(x)>0\), the graph has a local and absolute minimum at \((-\frac{1}{2}, 3)\). 2. The expression \(4x^2+4x+10\) is positive for every real \(x\), so \(f^{\prime\prime}(x)>0\) everywhere. The concavity never changes, so there are no inflection points. 3. Divide numerator and denominator of \(f^{\prime}\) by \(|x|\). For \(x\to\infty\), the limit is \(2\); for \(x\to-\infty\), the limit is \(-2\). 4. Complete the square: \(f(x)=\sqrt{(2x+1)^2+9}\). As \(x\to\infty\), \(f(x)-(2x+1)\to0\), so one asymptote is \(y=2x+1\). As \(x\to-\infty\), \(f(x)-(-2x-1)\to0\), so the other is \(y=-2x-1\).

Answer

1. Absolute minimum at \((-\frac{1}{2}, 3)\) 2. \(f^{\prime\prime}(x)>0\) for all \(x\), so there are no inflection points. 3. \(\lim_{x\to\infty}f^{\prime}(x)=2\) and \(\lim_{x\to-\infty}f^{\prime}(x)=-2\) 4. \(y=2x+1\) and \(y=-2x-1\)
53266912
Match each displayed graph \(G_1\), \(G_2\), and \(G_3\) with one function from the list. For each candidate function, use its derivative together with domain, intercepts, symmetry, and end behavior to justify the match. One function will not be used. - \(f_1(x)=2e^{-x^2}\) - \(f_2(x)=x^2e^{-x}\) - \(f_3(x)=\frac{e^x}{x}\) - \(f_4(x)=(x^2-1)e^{-x}\)
Figure for problem 532669

Hints

- Compare the domains and look for vertical asymptotes. - Identify zeros and y-intercepts. - Differentiate each candidate to locate critical numbers and determine increasing or decreasing intervals. - Analyze end behavior in both directions and check symmetry.

Solution

1. For \(f_4(x)=(x^2-1)e^{-x}\), the zeros are \(x=-1\) and \(x=1\), and the y-intercept is \(-1\). Also, \(f_4'(x)=(-x^2+2x+1)e^{-x}\), so its critical numbers are \(x=1\pm\sqrt{2}\). Together with \(f_4(x)\to0\) as \(x\to\infty\), these features match graph \(G_1\). 2. For \(f_3(x)=\frac{e^x}{x}\), the domain excludes \(x=0\), giving a vertical asymptote there. Since \(f_3'(x)=\frac{e^x(x-1)}{x^2}\), the function decreases for \(x<1\) on each part of its domain and increases for \(x>1\). It approaches \(0\) from below as \(x\to-\infty\) and grows without bound as \(x\to\infty\). These features match graph \(G_2\). 3. For \(f_1(x)=2e^{-x^2}\), \(f_1'(x)=-4xe^{-x^2}\). Thus, the function increases for \(x<0\), decreases for \(x>0\), and has a maximum at \((0,2)\). It is even and approaches \(0\) as \(x\to\pm\infty\), matching graph \(G_3\). 4. For \(f_2(x)=x^2e^{-x}\), \(f_2'(x)=x(2-x)e^{-x}\). The function is nonnegative, has a double zero at \(x=0\), and has a local maximum at \(x=2\). None of the displayed graphs has these features, so \(f_2\) is unused.

Answer

\(G_1\): \(f_4(x)=(x^2-1)e^{-x}\); \(G_2\): \(f_3(x)=\frac{e^x}{x}\); \(G_3\): \(f_1(x)=2e^{-x^2}\); unused: \(f_2(x)=x^2e^{-x}\)
53454512
The four panels show the graphs of a function \(f\) and its first three derivatives \(f'\), \(f''\), and \(f'''\). Match each panel to the correct function. Briefly justify your choices by comparing zeros, extrema, signs, and slopes.
Figure for problem 534545

Hints

- Zeros of a derivative correspond to horizontal tangents of the function one level above it. - Compare the sign of a possible derivative with where the preceding graph increases or decreases. - Apply the same derivative relationship repeatedly through the four panels.

Solution

1. Graph 4 has a local minimum at \(x=0\). Graph 3 is zero there and changes from negative to positive, so Graph 3 is the derivative of Graph 4. Thus Graph 4 is \(f\) and Graph 3 is \(f'\). 2. Graph 3 has local extrema near \(x=\pm1.6\). Graph 1 is zero at those x-values, and its sign matches where Graph 3 increases or decreases. Thus Graph 1 is \(f''\). 3. Graph 1 has local extrema at \(x=0\) and near \(x=\pm2.7\). Graph 2 is zero at those x-values, with signs matching the increase and decrease of Graph 1. Thus Graph 2 is \(f'''\).

Answer

Graph 1: \(f''\); Graph 2: \(f'''\); Graph 3: \(f'\); Graph 4: \(f\)
53486712
The figure shows the graph of a fourth-degree polynomial \(f\). The graph has a local minimum at \(x=-\frac{3}{2}\), a stationary inflection point \(S\) at \(x=3\), and an inflection point at \(I=(0, 2)\). The tangent line at \(I\) has slope \(2\). a) State the zeros of \(f'\) and \(f''\), including each zero’s multiplicity. b) Without calculating formulas, state the locations and types of the local extrema of \(f'\). Justify your answer. c) Determine whether the given information is sufficient to define \(f\) uniquely.
Figure for problem 534867

Hints

- Relate a local extremum and a stationary inflection point of \(f\) to zeros of its first derivative. - Relate inflection-point x-coordinates of \(f\) to extrema of its first derivative. - Write the first derivative in factored form from its known zeros and multiplicities. - Use the tangent slope to find the remaining factor, then use the point \(I=(0, 2)\).

Solution

1. At the local minimum \(x=-\frac{3}{2}\), \(f'\) has a simple zero. At the stationary inflection point \(x=3\), \(f'\) has a double zero. Since \(f'\) is cubic, these are all its zeros. 2. The inflection-point x-coordinates of \(f\) are \(x=0\) and \(x=3\), so these are the zeros of \(f''\). Each is simple because the concavity changes at both values. 3. At \(x=0\), \(f''\) changes from positive to negative, so \(f'\) has a local maximum. At \(x=3\), \(f''\) changes from negative to positive, so \(f'\) has a local minimum. 4. The zeros and multiplicities give \(f'(x)=k\left(x+\frac{3}{2}\right)(x-3)^2\). The tangent slope at \(I\) gives \(f'(0)=2\), so \(2=k\left(\frac{3}{2}\right)(9)\), which gives \(k=\frac{4}{27}\). Thus, \(f'\) is uniquely determined. Integrating gives \(f(x)=\frac{1}{27}x^4-\frac{2}{9}x^3+2x+C\). Since \(f(0)=2\), \(C=2\). Therefore, the information determines \(f\) uniquely.

Answer

a) Zeros of \(f'\): \(x=-\frac{3}{2}\), multiplicity \(1\); \(x=3\), multiplicity \(2\); zeros of \(f''\): \(x=0\) and \(x=3\), each with multiplicity \(1\). b) \(f'\) has a local maximum at \(x=0\) and a local minimum at \(x=3\). c) Yes. The zero structure and \(f'(0)=2\) determine \(f'\), and \(f(0)=2\) determines the constant of integration. In fact, \(f(x)=\frac{1}{27}x^4-\frac{2}{9}x^3+2x+2\).
55616812
A differentiable function satisfies \(f'(x)=-(x+2)(x-1)\). It is known that \(f(-2)=0\), \(f(-\tfrac12)=\tfrac94\), and \(f(1)=\tfrac92\). Without finding a formula for \(f\), give an exact graph blueprint: determine all local extrema, differentiate \(f'\) to find the inflection point, and state the monotonicity and concavity on every maximal interval.

Hints

- Sign-test the factored first derivative to classify the extrema. - Differentiate \(f'\) to obtain \(f''\), then find its sign change. - The supplied function values place each landmark vertically; no antiderivative is needed.

Solution

1. The zeros of \(f'\) are \(x=-2\) and \(x=1\). Since \(f'\) is a downward-opening quadratic, it is negative on \(( -\infty,-2)\), positive on \((-2,1)\), and negative on \((1,\infty)\). 2. Thus \((-2,0)\) is a local minimum and \((1,\tfrac92)\) is a local maximum. 3. Differentiate the given derivative: \(f''(x)=-2x-1\). Solve \(f''(x)=0\): \(x=-\tfrac12\). The sign changes from positive to negative, so \((-\tfrac12,\tfrac94)\) is an inflection point. 4. Concavity is up on \(( -\infty,-\tfrac12)\) and down on \((-\tfrac12,\infty)\). 5. Combining both derivatives gives maximal behavior intervals: decreasing/concave up on \(( -\infty,-2)\); increasing/concave up on \((-2,-\tfrac12)\); increasing/concave down on \((-\tfrac12,1)\); decreasing/concave down on \((1,\infty)\).

Answer

Local min \((-2,0)\); inflection \((-1/2,9/4)\); local max \((1,9/2)\). Behavior: ↓/CU on \(( -\infty,-2)\), ↑/CU on \((-2,-1/2)\), ↑/CD on \((-1/2,1)\), ↓/CD on \((1,\infty)\).
55616912
Let \(f\) be differentiable with \(f(0)=0\) and \(f'(x)=(x^2-1)(x^2-4)\). The end behavior is \(f(x)\to-\infty\) as \(x\to-\infty\) and \(f(x)\to\infty\) as \(x\to\infty\). Give a complete exact graph blueprint without finding a formula for \(f\): a) classify all four critical numbers; b) differentiate \(f'\) and find all inflection-point x-coordinates; c) state every maximal monotonicity and concavity interval; and d) list the significant x-values in left-to-right order, including the anchor \((0,0)\), so another student could sketch the graph from your blueprint.

Hints

- Use the ordered simple zeros of \(f'\) to build its sign chart. - Differentiate \(f'\) before building the concavity chart. - Merge the two ordered breakpoint lists only after both charts are correct. - The anchor and stated end behavior place the qualitative graph; no integration is needed.

Solution

1. The critical numbers are \(-2,-1,1,2\). Because all four zeros of \(f'\) are simple, its sign alternates. Since \(f'>0\) for large \(|x|\), the sign pattern is \(+,-,+,-,+\). 2. Therefore \(x=-2\) and \(x=1\) are local maxima, while \(x=-1\) and \(x=2\) are local minima. The maximal increasing intervals are \(( -\infty,-2)\), \((-1,1)\), and \((2,\infty)\); the maximal decreasing intervals are \((-2,-1)\) and \((1,2)\). 3. Differentiate: \(f''(x)=4x^3-10x=2x(2x^2-5)\). Thus the inflection inputs are \(-\sqrt{5/2},0,\sqrt{5/2}\). Each zero is simple, so concavity changes at each one. 4. Testing signs gives concave down on \(( -\infty,-\sqrt{5/2})\), concave up on \((-\sqrt{5/2},0)\), concave down on \((0,\sqrt{5/2})\), and concave up on \((\sqrt{5/2},\infty)\). 5. Left-to-right significant inputs are \(-2,-\sqrt{5/2},-1,0,1,\sqrt{5/2},2\). At \(x=0\), the graph passes through \((0,0)\) and changes concavity. Combine this order with the stated end behavior and interval directions.

Answer

Local maxima at \(x=-2,1\); local minima at \(x=-1,2\). Increasing on \(( -\infty,-2)\), \((-1,1)\), \((2,\infty)\); decreasing on \((-2,-1)\), \((1,2)\). Inflection inputs \(-\sqrt{5/2},0,\sqrt{5/2}\). Concave down on \(( -\infty,-\sqrt{5/2})\) and \((0,\sqrt{5/2})\); concave up on \((-\sqrt{5/2},0)\) and \((\sqrt{5/2},\infty)\). Significant order: \(-2,-\sqrt{5/2},-1,(0,0),1,\sqrt{5/2},2\), with left end down and right end up.

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