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(x+y+1)(x+y-1)=______.
人气:203 ℃ 时间:2020-06-16 21:34:35
解答
(x+y+1)(x+y-1),
=[(x+y)+1][(x+y)-1],
=(x+y)2-12
=x2+2xy+y2-1.
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