The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -1.2718\\[1 em]x_2 &= 2.3965\\[1 em]x_3 &= -2.6247 \end{aligned} $$Polynomial $ 2x^3+3x^2-12x-16 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.