Answer
$$\frac{a-1}{a}$$
Work Step by Step
Simplifying using the rules of fractions, we find:
$$\frac{1-a^{-2}}{1+\frac{1}{a}} \\ \frac{\frac{a^2-1}{a^2}}{\frac{a+1}{a}} \\ \frac{a^2-1}{a\left(a+1\right)} \\ \frac{\left(a+1\right)\left(a-1\right)}{a\left(a+1\right)}\\ \frac{a-1}{a}$$
