The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.3111+0.2287i\\[1 em]x_2 &= 0.3111-0.2287i\\[1 em]x_3 &= -0.3111+0.2287i\\[1 em]x_4 &= -0.3111-0.2287i \end{aligned} $$Polynomial $ 45x^4-4x^2+1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.