The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -1.2031\\[1 em]x_2 &= 0.4016+0.0706i\\[1 em]x_3 &= 0.4016-0.0706i \end{aligned} $$Polynomial $ 5x^3+2x^2-4x+1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.