The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.4917\\[1 em]x_2 &= -1.7824\\[1 em]x_3 &= 1.5083\\[1 em]x_4 &= 3.7824 \end{aligned} $$Polynomial $ x^4-4x^3-2x^2+12x-5 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.