The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 8\\[1 em]x_2 &= 6 \end{aligned} $$The solutions of $ -x^2+14x-48 = 0 $ are: $ x = 6 ~ \text{and} ~ x = 8$.
You can use step-by-step quadratic equation solver to see a detailed explanation on how to solve this quadratic equation.