The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -1.3146\\[1 em]x_2 &= 1.1573+1.3052i\\[1 em]x_3 &= 1.1573-1.3052i \end{aligned} $$Polynomial $ x^3-x^2+4 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.