The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 2+4i\\[1 em]x_2 &= 2-4i\\[1 em]x_3 &= 6+5i\\[1 em]x_4 &= 6-5i \end{aligned} $$Polynomial $ x^4-16x^3+129x^2-484x+1220 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.