The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.43i\\[1 em]x_2 &= -0.43i\\[1 em]x_3 &= 3.2886i\\[1 em]x_4 &= -3.2886i \end{aligned} $$Polynomial $ x^4+11x^2+2 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.