The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -2.3247\\[1 em]x_2 &= -0.3376+0.5623i\\[1 em]x_3 &= -0.3376-0.5623i \end{aligned} $$Polynomial $ x^3+3x^2+2x+1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.