The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.6829\\[1 em]x_2 &= -0.5081+1.4556i\\[1 em]x_3 &= -0.5081-1.4556i \end{aligned} $$Polynomial $ 3x^3-2x^2+2x-12 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.