X2+Y2-X2+2xy-Y2+2xy-2Y2Y2Y2, simplified as:

4 xy-2 y 2, this is a simplified form of molecule, so the denominator in the topic is 4 y.

The numerator and denominator are divided by y at the same time to get 2(2x-y)/5.

The result is: 5.

I hope I can help you solve the problem. If you are satisfied, please accept it. I wish you progress in your study. O(∩_∩)O Thank you ~