The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 3.3179\\[1 em]x_2 &= -0.159+1.0147i\\[1 em]x_3 &= -0.159-1.0147i \end{aligned} $$Polynomial $ 2x^3-6x^2-7 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.