Answer
$\displaystyle \frac{x-4}{x+4} $
Work Step by Step
Simplifying Rational Expressions
1. Factor the numerator and the denominator completely.
2. Divide both the numerator and the denominator by any common factors.
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Numerator: fully factored
Denominator: recognize a difference of squares
$x^{2}-4^{2}=(x+4)(x-4)$
Expression = $\displaystyle \frac{(x-4)^{2}}{(x+4)(x-4)}$
... divide both with the common factor: $(x-4)$
Expression = $\displaystyle \frac{x-4}{x+4} $
