The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 3.1958\\[1 em]x_2 &= -0.0979+0.785i\\[1 em]x_3 &= -0.0979-0.785i \end{aligned} $$Polynomial $ -x^3+3x^2+2 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.