The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.3572\\[1 em]x_2 &= -0.6786+1.1754i\\[1 em]x_3 &= -0.6786-1.1754i \end{aligned} $$Polynomial $ 2x^3-5 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.