1/(x2-2xy+y2)+1/(x2+2xy+y2)=1.那位懂的帮帮忙.

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1/(x2-2xy+y2)+1/(x2+2xy+y2)=1.那位懂的帮帮忙.1/(x2-2xy+y2)+1/(x2+2xy+y2)=1.那位懂的帮帮忙.1/(x2-2xy+y2)+1/(x2+2xy+

1/(x2-2xy+y2)+1/(x2+2xy+y2)=1.那位懂的帮帮忙.
1/(x2-2xy+y2)+1/(x2+2xy+y2)=1.那位懂的帮帮忙.

1/(x2-2xy+y2)+1/(x2+2xy+y2)=1.那位懂的帮帮忙.
1/(x2-2xy+y2)+1/(x2+2xy+y2)
=1/(x-y)2+1/(x+y)2
=(x+y)2/(x-y)2(x+y)2+(x-y)2/(x-y)2(x+y)2
=[(x+y)2+(x-y)2]/(x-y)2(x+y)2
=2(x2+y2)/(x2-y2)2
这个式子不是恒等式

题目写错了,你取x=2,y=1就是反例