Answer
$$\frac{\left(a+b\right)\left(a-b\right)}{a^2+b^2}$$
Work Step by Step
Using the rules of fractions, we find:
$$\frac{a^2-b^2}{a^2+b^2} \\ \frac{\left(a+b\right)\left(a-b\right)}{a^2+b^2}$$
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