=x(x-y)/(x+y)(x-y)+y(x+y)/(x+y)(x-y)-y²/(x+y)(x-y)
=[x(x-y)+y(x+y)-y²]/(x+y)(x-y)
=x²/(x²-y²)恩恩，我看看请采纳，谢谢然后，还有，我自己算算，五分之x=三分之y？？？？？？？？？？？？？？？？哦，x/5=y/3设x=5k，则y=3k原式=x²/(x²-y²) =25k²/(25k²-9k²)=25/16