x-y/x^2-2xy+y^2-xy+y^2/x^2-y^2先化简再求值,其中（x-2）^2+|y-3|=0
问题描述：
x-y/x^2-2xy+y^2-xy+y^2/x^2-y^2先化简再求值,其中（x-2）^2+|y-3|=0
答
(x-y)/(x^2-2xy+y^2)-(xy+y^2)/(x^2-y^2)
=(x-y)/(x-y)²-y(x+y)/(x+y)(x-y)
=1/(x-y)-y/(x-y)
=(1-y)/(x-y)
∵(x-2)²+|y-3|=0
∴(x-2)²=0 |y-3|=0
即x=2 y=3
∴原式=(1-3)/(2-3)=2