Answer
$\frac{1}{49a^2}$
Work Step by Step
We start with the given expression: $(7a)^{-2}$
The negative exponent rule states that for every nonzero number $a$ and integer $n$, $a^{-n}=\frac{1}{a^n}$. We use this rule to rewrite the expression: $\frac{1}{(7a)^2}$
To raise a product to a power, we raise each factor to the power and multiply: $\frac{1}{7^2a^2}$
We expand the constant power: $\frac{1}{7\times7a^2}=\frac{1}{49a^2}$
