Simplifying Expressions with Exponents

[soulofeternity]

Problem- (x^-2-y^-2)/(x^-1-y^-1)

The book doesn't list a full answer for this problem. All it lists is the numerator as being x+y.
I really don't understand what I'm doing wrong. I've tried flipping it, turning everything into fractions, and really anything else that I can think of but I still can't get the numerator to end up like that.

 

[hypoid]

(x^-2-y^-2)/(x^-1-y^-1)=[(y^2-x^2)/(y^2*x^2)]*[(y*x)/(y-x)]=(y+x)/yx