The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.6805\\[1 em]x_2 &= -0.118+0.6187i\\[1 em]x_3 &= -0.118-0.6187i \end{aligned} $$Polynomial $ 9x^3-13x^2-6 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.