The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 1.3953\\[1 em]x_2 &= -1.7451\\[1 em]x_3 &= 0.4249+1.0255i\\[1 em]x_4 &= 0.4249-1.0255i \end{aligned} $$Polynomial $ 2x^4-x^3-3x^2+5x-6 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.