You can think of a negative exponent as one that's been "misplaced" and needs to be moved back onto the correct side of its fraction. So if I gave you x-2, simplifying the expression is a matter of moving the exponent part from the numerator to the denominator and making the exponent positive so
Similary, if you had an exponent in the denominator, it would move to the numerator.
Just like any other exponent simplification problem you should always be very wary of addition. If I asked you to simplify
|x2 + y2|
the correct answer would be
y3(x2 + y2)
The denominator is being divided into the entire numerator so when you "fix" the negative exponent, you have to apply it to the entire numerator, not just, for example, the y part or the x part