The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.3473\\[1 em]x_2 &= 1.5321\\[1 em]x_3 &= -1.8794 \end{aligned} $$Polynomial $ -x^3+3x-1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.