The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.7321\\[1 em]x_2 &= -1.7321\\[1 em]x_3 &= 0.5+0.866i\\[1 em]x_4 &= 0.5-0.866i \end{aligned} $$Polynomial $ x^4-x^3-2x^2+3x-3 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.