The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.7821\\[1 em]x_2 &= 1.32\\[1 em]x_3 &= -1.0928+0.2502i\\[1 em]x_4 &= -1.0928-0.2502i\\[1 em]x_5 &= 0.0418+1.52i\\[1 em]x_6 &= 0.0418-1.52i \end{aligned} $$Polynomial $ x^6-4x^2-x+3 $ has no rational roots that can be found using Rational Root Test, so the roots were found using Newton method.