The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.0523\\[1 em]x_2 &= -0.3387+0.7733i\\[1 em]x_3 &= -0.3387-0.7733i \end{aligned} $$Polynomial $ 8x^3-3x^2-6 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.