The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -1.0328\\[1 em]x_2 &= 1.1648\\[1 em]x_3 &= 4.83\\[1 em]x_4 &= 0.019+1.1732i\\[1 em]x_5 &= 0.019-1.1732i \end{aligned} $$Polynomial $ x^5-5x^4+x^3-x^2-x+8 $ has no rational roots that can be found using Rational Root Test, so the roots were found using Newton method.