The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.3264\\[1 em]x_2 &= -1.4691\\[1 em]x_3 &= -2.6073 \end{aligned} $$Polynomial $ -4x^3-15x^2-10x+5 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.