2xy/x平方-y平方-x/x+y+y/y-x,其中x=3、y=2 先化简再求值

问题描述:

2xy/x平方-y平方-x/x+y+y/y-x,其中x=3、y=2 先化简再求值

2xy/x平方-y平方-x/x+y+y/y-x
=[2xy-x(x-y)-y(x+y)]/(x+y)(x-y)
=(2xy-x²+xy-xy-y²)/(x+y)(x-y)
=(2xy-x²-y²)/(x+y)(x-y)
=-(x-y)²/(x+y)(x-y)
=(y-x)/(x+y)
=(2-3)/(3+2)
=-1/5
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