The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.3449\\[1 em]x_2 &= 0.5472\\[1 em]x_3 &= -0.8152 \end{aligned} $$Polynomial $ -13x^3+x^2+7x-2 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.