The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.4534\\[1 em]x_2 &= -0.2267+1.4677i\\[1 em]x_3 &= -0.2267-1.4677i \end{aligned} $$Polynomial $ x^3+2x-1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.