The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.2134+0.9349i\\[1 em]x_2 &= 0.2134-0.9349i\\[1 em]x_3 &= -0.2134+1.7936i\\[1 em]x_4 &= -0.2134-1.7936i \end{aligned} $$Polynomial $ x^4+4x^2-x+3 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.