The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -1.8165\\[1 em]x_2 &= 30.9745\\[1 em]x_3 &= 0.921+1.6451i\\[1 em]x_4 &= 0.921-1.6451i \end{aligned} $$Polynomial $ x^4-31x^3+x^2-200 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.