The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -1.5311\\[1 em]x_2 &= -1.5311\\[1 em]x_3 &= 6.5311\\[1 em]x_4 &= 6.5311 \end{aligned} $$Polynomial $ x^4-10x^3+5x^2+100x+100 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.