The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -1.461\\[1 em]x_2 &= 14.2864\\[1 em]x_3 &= 1.5873+2.7635i\\[1 em]x_4 &= 1.5873-2.7635i \end{aligned} $$Polynomial $ x^4-16x^3+30x^2-64x-212 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.