Answer
$\color{blue}{x^2-4x+16}$
Work Step by Step
The given expression is equivalent to:
$=\dfrac{x^3+4^3}{x+4}$
Factor the numerator and the denominator then cancel the common factors. Factor the numerator using the formula $a^3+b^3=(a+b)(a^2-ab+b^2)$ with $a=x$ and $b=4$.
:
$\require{cancel}
=\dfrac{(x+4)(x^2-4x+16)}{x+4}
\\=\dfrac{\cancel{(x+4)}(x^2-4x+16)}{\cancel{x+4}}
\\=\color{blue}{x^2-4x+16}$
