The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 9.1231\\[1 em]x_2 &= 0.8769 \end{aligned} $$The solutions of $ -x^2+10x-8 = 0 $ are: $ x = 5-\sqrt{ 17 } ~ \text{and} ~ x = 5+\sqrt{ 17 }$.
You can use step-by-step quadratic equation solver to see a detailed explanation on how to solve this quadratic equation.