(x-y分之1+x+y分之1)除以x的平方-y的平方分之x的平方y
问题描述：
(x-y分之1+x+y分之1)除以x的平方-y的平方分之x的平方y
答
解
[1/(x-y)+1/(x+y)]÷[x²y/(x²-y²)]————是这个吗?
=[1/(x-y)+1/(x+y)]×[(x-y)(x+y)/x²y]
=[(x+y)/x²y+(x-y)/x²y]
=(x+y+x-y)/x²y
=2x/x²y
=2/xy