The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.8347\\[1 em]x_2 &= -0.6272\\[1 em]x_3 &= -2.3962\\[1 em]x_4 &= 3.1888 \end{aligned} $$Polynomial $ x^4-x^3-8x^2+2x+4 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.