The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -1.7134\\[1 em]x_2 &= 3.5147\\[1 em]x_3 &= 0.0993+0.8089i\\[1 em]x_4 &= 0.0993-0.8089i \end{aligned} $$Polynomial $ x^4-2x^3-5x^2-4 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.