Find $ \left(x+6\right)^2 $ using formula.

$$ (A + B)^2 = \color{blue}{A^2} + 2 \cdot A \cdot B + \color{red}{B^2} $$

where $ A = \color{blue}{ x } $ and $ B = \color{red}{ 6 }$.

$$ \begin{aligned}\left(x+6\right)^2 = \color{blue}{x^2} +2 \cdot x \cdot 6 + \color{red}{6^2} = x^2+12x+36\end{aligned} $$

Multiply each term of $ \left( \color{blue}{x+13}\right) $ by each term in $ \left( x^2+12x+36\right) $.

$$ \left( \color{blue}{x+13}\right) \cdot \left( x^2+12x+36\right) = x^3+12x^2+36x+13x^2+156x+468 $$

Combine like terms:

$$ x^3+ \color{blue}{12x^2} + \color{red}{36x} + \color{blue}{13x^2} + \color{red}{156x} +468 = x^3+ \color{blue}{25x^2} + \color{red}{192x} +468 $$

Multiply each term of $ \left( \color{blue}{x^3+25x^2+192x+468}\right) $ by each term in $ \left( x-2\right) $.

$$ \left( \color{blue}{x^3+25x^2+192x+468}\right) \cdot \left( x-2\right) = x^4-2x^3+25x^3-50x^2+192x^2-384x+468x-936 $$

Combine like terms:

$$ x^4 \color{blue}{-2x^3} + \color{blue}{25x^3} \color{red}{-50x^2} + \color{red}{192x^2} \color{green}{-384x} + \color{green}{468x} -936 = \\ = x^4+ \color{blue}{23x^3} + \color{red}{142x^2} + \color{green}{84x} -936 $$

Multiply each term of $ \left( \color{blue}{x^4+23x^3+142x^2+84x-936}\right) $ by each term in $ \left( x-8\right) $.

$$ \left( \color{blue}{x^4+23x^3+142x^2+84x-936}\right) \cdot \left( x-8\right) = \\ = x^5-8x^4+23x^4-184x^3+142x^3-1136x^2+84x^2-672x-936x+7488 $$

Combine like terms:

$$ x^5 \color{blue}{-8x^4} + \color{blue}{23x^4} \color{red}{-184x^3} + \color{red}{142x^3} \color{green}{-1136x^2} + \color{green}{84x^2} \color{orange}{-672x} \color{orange}{-936x} +7488 = \\ = x^5+ \color{blue}{15x^4} \color{red}{-42x^3} \color{green}{-1052x^2} \color{orange}{-1608x} +7488 $$