The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.3377\\[1 em]x_2 &= 1.3075\\[1 em]x_3 &= -0.8226+1.2603i\\[1 em]x_4 &= -0.8226-1.2603i \end{aligned} $$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.