How to Simplify Negative Exponents with Variables
Distributing with negative exponents means that you’ll have fractional answers. A base that has a negative exponent can be changed to a fraction. The base and the exponent become the denominator, but the exponent loses its negative sign in the process. You then cap it all off with a 1 in the numerator.
The following steps show how a negative exponent can lead to a fraction.

Distribute
Here’s what you’ll get.

Add the exponents.

The factor of b with the 0 exponent becomes 1.

Change terms with negative exponents to fractions.