The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -4.1516\\[1 em]x_2 &= 0.5758+2.3344i\\[1 em]x_3 &= 0.5758-2.3344i \end{aligned} $$Polynomial $ x^3+3x^2+x+24 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.