The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.1509\\[1 em]x_2 &= -1.0755+1.5228i\\[1 em]x_3 &= -1.0755-1.5228i \end{aligned} $$Polynomial $ x^3+x^2+x-4 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.