The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 2.2056\\[1 em]x_2 &= -0.1028+0.6655i\\[1 em]x_3 &= -0.1028-0.6655i \end{aligned} $$Polynomial $ x^3-2x^2-1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.