The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.2488\\[1 em]x_2 &= -0.2244+0.7143i\\[1 em]x_3 &= -0.2244-0.7143i \end{aligned} $$Polynomial $ 10x^3-8x^2-7 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.