The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -1.6465\\[1 em]x_2 &= -0.3434+0.2907i\\[1 em]x_3 &= -0.3434-0.2907i \end{aligned} $$Polynomial $ 3x^3+7x^2+4x+1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.