Answer
$(-5)^{-2} =\dfrac{1}{(-5)^2}=\dfrac{1}{25}$
Work Step by Step
RECALL:
The negative-exponent rule of exponents states that:
$a^{-m} =\dfrac{1}{a^m}$ and $\dfrac{1}{a^{-m}} = a^m$, where $a \ne 0$.
Use the negative-exponent rule to find:
$(-5)^{-2} =\dfrac{1}{(-5)^2}=\dfrac{1}{25}$