若xy=1,则(x+1分之1)+(y+1分之一)=?
问题描述：
若xy=1,则(x+1分之1)+(y+1分之一)=?
答
（x+1）/1+（y+1）/1=（x+1+y+1）/（xy+x+y+1）将xy=1代入得（x+1）/1+（y+1）/1=1
答
(x+1分之1)+(y+1分之一)=(x+y+2)/(x+y+xy+1)=1
答
(x+1分之1)+(y+1分之一)
=(y+1+x+1)/(x+1)(y+i)
=x+y+2/(xy+x+y+1)
=x+y+2/(1+x+y+1)
=1