1、如果1/x+1/y=2,求3x+2xy+3y/2x-3xy+2y的值
问题描述：
1、如果1/x+1/y=2,求3x+2xy+3y/2x-3xy+2y的值
2、(1+1/2+1/3+1/4)*(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)*(1/2+1/3+1/4)
答
1题：1/x+1/y=2
∴(x+y)/xy=2
∴x+y=2xy
∴原式＝[3（x+y)+2xy]/[2(x+y)-3xy]
=(8xy)/(xy)=8
2题：原式＝、(1+1/2+1/3+1/4)*(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)*(1+1/2+1/3+1/4)+（1+1/2+1/3+1/4+1/5)
＝（1+1/2+1/3+1/4）*[(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)+（1+1/2+1/3+1/4+1/5)
=-(1+1/2+1/3+1/4)+(1+1/2+1/3+1/4+1/5)
=1/5