The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.6274\\[1 em]x_2 &= -2.3137+0.4211i\\[1 em]x_3 &= -2.3137-0.4211i \end{aligned} $$Polynomial $ -x^3-3x^2+2x+9 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.