1/x+1/y=(x+y)/xy=5
所以x+y=5xy
所以原式=[2(x+y)-3xy]/[(x+y)+2xy]
=[2(5xy)-3xy]/[(5xy)+2xy]
=7xy/7xy
=12种上下除以xy原式=(2/x+2/y-3(/(1/x+2+1/y)=(10-3)/(5+2)=1