The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.5586\\[1 em]x_2 &= 5.0458\\[1 em]x_3 &= 7.3878 \end{aligned} $$Polynomial $ 640x^3-8955x^2+36260x-37184 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.