The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -0.3301\\[1 em]x_2 &= 0.165+0.939i\\[1 em]x_3 &= 0.165-0.939i \end{aligned} $$Polynomial $ 10x^3+8x+3 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.