The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -3.0397\\[1 em]x_2 &= 2.0198+5.0199i\\[1 em]x_3 &= 2.0198-5.0199i \end{aligned} $$Polynomial $ -x^3+x^2-17x-89 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.