The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.2865\\[1 em]x_2 &= -1.1987\\[1 em]x_3 &= 2.9122 \end{aligned} $$Polynomial $ -x^3+2x^2+3x-1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.