The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.3294\\[1 em]x_2 &= -1.5396\\[1 em]x_3 &= 0.6051+1.2671i\\[1 em]x_4 &= 0.6051-1.2671i \end{aligned} $$Polynomial $ x^4+3x-1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.