The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.3129\\[1 em]x_2 &= 1.6871\\[1 em]x_3 &= 1+2.9107i\\[1 em]x_4 &= 1-2.9107i \end{aligned} $$Polynomial $ x^4-4x^3+14x^2-20x+5 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.