The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.7979\\[1 em]x_2 &= -4.4117\\[1 em]x_3 &= 5.1138 \end{aligned} $$Polynomial $ 4x^3-6x^2-88x+72 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.