The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -0.3977\\[1 em]x_2 &= 1.5592\\[1 em]x_3 &= 4.8385 \end{aligned} $$Polynomial $ -x^3+6x^2-5x-3 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.