Find all the roots of the polynomial f(x) = x^4-5x^3+5x^2+17x-42 - x^4 + 5x^3 - 4x^2 - 16x + 20.
+592 x4 - 5x3 + 5x2 + 17x - 42 - x4 + 5x3 - 4x2 - 16x + 20
= x4 - x4 - 5x3 + 5x3 + 5x2 - 4x2 + 17x - 16x - 42 + 20
= x2 + x - 22
\(x = \frac{-1 + \sqrt{89}}{2}\)
\(x = \frac{-1 - \sqrt{89}}{2} \)
