The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.5827\\[1 em]x_2 &= -0.2913+0.3601i\\[1 em]x_3 &= -0.2913-0.3601i \end{aligned} $$Polynomial $ 8x^3-x-1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.