x-y分之1减x+y分之1等于多少?

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x-y分之1减x+y分之1等于多少?
x-y分之1减x+y分之1等于多少?

x-y分之1减x+y分之1等于多少?
1/(x-y)- 1/(x+y)
原式=(x+y)/(x-y)(x+y)- (x-y)/(x-y)(x+y)
=(x+y)-(x-y)/(x-y)(x+y)
=x+y-x+y/(x-y)(x+y)
=2y/(x-y)(x+y)【也可写成2y/x^2-y^2,这是平方差公式,楼下的是错的,(x-y)^2分解成
x^2-2xy+y^2,与原式不符.2y/(x-y)(x+y)才是正确答案】