The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -1.0955\\[1 em]x_2 &= 1.0955\\[1 em]x_3 &= 2.4495\\[1 em]x_4 &= -2.4495 \end{aligned} $$Polynomial $ 5x^4-36x^2+36 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.