The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -1.3985\\[1 em]x_2 &= -28.6015 \end{aligned} $$The solutions of $ x^2+30x+40 = 0 $ are: $ x = -15-\sqrt{ 185 } ~ \text{and} ~ x = -15+\sqrt{ 185 }$.
You can use step-by-step quadratic equation solver to see a detailed explanation on how to solve this quadratic equation.