The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 3.4142\\[1 em]x_2 &= 0.5858 \end{aligned} $$The solutions of $ -3x^2+12x-6 = 0 $ are: $ x = 2-\sqrt{ 2 } ~ \text{and} ~ x = 2+\sqrt{ 2 }$.
You can use step-by-step quadratic equation solver to see a detailed explanation on how to solve this quadratic equation.