The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.4142\\[1 em]x_2 &= -1.4142\\[1 em]x_3 &= 1.291i\\[1 em]x_4 &= -1.291i \end{aligned} $$Polynomial $ 3x^4-x^2-10 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.