The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 3.1498\\[1 em]x_2 &= -1.5749+2.7278i\\[1 em]x_3 &= -1.5749-2.7278i \end{aligned} $$Polynomial $ 4x^3-125 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.