The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.6506\\[1 em]x_2 &= -0.8253+1.5469i\\[1 em]x_3 &= -0.8253-1.5469i \end{aligned} $$Polynomial $ 2x^3+2x^2+4x-4 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.