The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -2.1248\\[1 em]x_2 &= 0.7291+0.7528i\\[1 em]x_3 &= 0.7291-0.7528i \end{aligned} $$Polynomial $ 3x^3+2x^2-6x+7 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.