The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 2.0801\\[1 em]x_2 &= -1.04+1.8014i\\[1 em]x_3 &= -1.04-1.8014i \end{aligned} $$Polynomial $ x^3-9 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.