The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.5332\\[1 em]x_2 &= 0.2334+1.9227i\\[1 em]x_3 &= 0.2334-1.9227i \end{aligned} $$Polynomial $ -x^3+x^2-4x+2 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.