The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 2\\[1 em]x_2 &= -2 \end{aligned} $$Step 1:
Combine like terms:
$$ x^2 \color{blue}{-12} + \color{blue}{8} = x^2 \color{blue}{-4} $$Step 2:
The solutions of $ x^2-4 = 0 $ are: $ x = -2 ~ \text{and} ~ x = 2$.
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