The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.2419\\[1 em]x_2 &= -1.621+1.1826i\\[1 em]x_3 &= -1.621-1.1826i \end{aligned} $$Polynomial $ x^3+2x^2-5 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.