The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.8816\\[1 em]x_2 &= 1.5592+4.0867i\\[1 em]x_3 &= 1.5592-4.0867i \end{aligned} $$Polynomial $ x^3-5x^2+25x-36 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.