The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -4.2014\\[1 em]x_2 &= -1.6493+1.3861i\\[1 em]x_3 &= -1.6493-1.3861i \end{aligned} $$Polynomial $ 4x^3+30x^2+74x+78 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.