The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= \frac{ 10 }{ 7 }+\frac{ 2 \sqrt{ 3}}{ 7 }i\\[1 em]x_2 &= \frac{ 10 }{ 7 }-2 \frac{\sqrt{ 3 }}{ 7 }i \end{aligned} $$Step 1:
Combine like terms:
$$ \color{blue}{x^2} \color{blue}{-8x^2} +20x-16 = \color{blue}{-7x^2} +20x-16 $$Step 2:
The solutions of $ -7x^2+20x-16 = 0 $ are: $ x = \dfrac{ 10 }{ 7 }+\dfrac{ 2 \sqrt{ 3}}{ 7 }i ~ \text{and} ~ x = \dfrac{ 10 }{ 7 }-\dfrac{ 2 \sqrt{ 3}}{ 7 }i$.
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