The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.2833\\[1 em]x_2 &= 0.7705\\[1 em]x_3 &= -3.0539 \end{aligned} $$Polynomial $ 3x^3+6x^2-9x+2 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.