第二题怎么写，求学霸解答
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x/(x-y)·y^2/(x+y)-x^4y/(x^4-y^4)÷x^2/(x^2+y^2)
=xy^2/(x^2-y^2)-x^4y/[(x^2+y^2)(x^2-y^2)]·(x^2+y^2)/x^2
=xy^2/(x^2-y^2)-x^2y/(x^2-y^2)
=(xy^2-x^2y)/(x^2-y^2)
=xy(y-x)/[(x+y)(x-y)]
=-xy(x-y)/[(x+y)(x-y)]
=-xy/(x+y)
=1
-xy=x+y
1/x+1/y
=y/xy+x/xy
=(x+y)/xy
=-1
=xy^2/(x^2-y^2)-x^4y/[(x^2+y^2)(x^2-y^2)]·(x^2+y^2)/x^2
=xy^2/(x^2-y^2)-x^2y/(x^2-y^2)
=(xy^2-x^2y)/(x^2-y^2)
=xy(y-x)/[(x+y)(x-y)]
=-xy(x-y)/[(x+y)(x-y)]
=-xy/(x+y)
=1
-xy=x+y
1/x+1/y
=y/xy+x/xy
=(x+y)/xy
=-1
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