The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.5243\\[1 em]x_2 &= -0.5243\\[1 em]x_3 &= 2.6972i\\[1 em]x_4 &= -2.6972i \end{aligned} $$Polynomial $ -x^4-7x^2+2 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.