The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 2+i\\[1 em]x_2 &= 2-i\\[1 em]x_3 &= 2+i\\[1 em]x_4 &= 2-i \end{aligned} $$Polynomial $ x^4-8x^3+26x^2-40x+25 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.