The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.2624\\[1 em]x_2 &= -0.3826\\[1 em]x_3 &= 1.2452 \end{aligned} $$Polynomial $ 8x^3-9x^2-2x+1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.