若2/x+2/y=1,则（2x-xy+2y）/（3x+5xy+3y）=?
问题描述：
若2/x+2/y=1,则（2x-xy+2y）/（3x+5xy+3y）=?
答
2/x+2/y=1
所以
1/x+1/y=1/2
所以（2x-xy+2y）/（3x+5xy+3y)
=(2/y-1+2/x)/(3/y+5+3/x)
=(2(1/x+1/y)-1)/(3(1/x+1/y)+5)
=(2*1/2-1)/(3*1/2+5)
=0
答
0
2/x+2/y=1两边同乘xy得2x+2y=xy
2x-xy+2y=0 分母为0所以答案为0
答
2/x+2/y=1
2(x+y)/xy=1
2(x+y)=xy
(x+y)=xy/2
(2x-xy+2y)/(3x+5xy+3y)
=(xy-xy)/(13xy/2)
=0