The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.2086\\[1 em]x_2 &= -0.8764\\[1 em]x_3 &= -2.8322 \end{aligned} $$Polynomial $ 2x^3+5x^2-4x-6 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.