Find all zeros of \(f(x)=x^5-2x^4-4x^3+8x^2+3x-6\).
Test possible integer zeros and use synthetic division repeatedly until a quadratic equation remains.
Hints
- Start by testing integer factors of the constant term.
- Use each confirmed zero as a synthetic value.
- After each zero remainder, continue with the quotient coefficients.
- Stop when the quotient is quadratic, then solve that equation exactly.
Solution
1. Possible integer zeros are among \(\pm1\), \(\pm2\), \(\pm3\), and \(\pm6\). Testing identifies \(x=1\), \(x=-1\), and \(x=2\) as zeros.
2. Use synthetic value \(1\) with coefficients \(1,-2,-4,8,3,-6\). Bring down \(1\); multiply and add successively to obtain \(-1,-5,3,6\), then remainder \(0\). The quotient is \(x^4-x^3-5x^2+3x+6\).
3. Use synthetic value \(-1\) with coefficients \(1,-1,-5,3,6\). Bring down \(1\); multiply and add successively to obtain \(-2,-3,6\), then remainder \(0\). The quotient is \(x^3-2x^2-3x+6\).
4. Use synthetic value \(2\) with coefficients \(1,-2,-3,6\). Bring down \(1\); multiply and add successively to obtain \(0,-3\), then remainder \(0\). The quotient is \(x^2-3\).
5. Solve \(x^2-3=0\): \(x=-\sqrt{3}\) or \(x=\sqrt{3}\).
6. Therefore, the zeros are \(x=-\sqrt{3}\), \(x=-1\), \(x=1\), \(x=\sqrt{3}\), and \(x=2\).
Answer
The zeros are \(x=-\sqrt{3}\), \(x=-1\), \(x=1\), \(x=\sqrt{3}\), and \(x=2\).