The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -2.2646\\[1 em]x_2 &= -0.0344+1.0846i\\[1 em]x_3 &= -0.0344-1.0846i \end{aligned} $$Polynomial $ 3x^3+7x^2+4x+8 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.