The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 17.055\\[1 em]x_2 &= -0.0275+0.9682i\\[1 em]x_3 &= -0.0275-0.9682i \end{aligned} $$Polynomial $ -x^3+17x^2+16 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.