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(x-y+9)(x+y-9)
人气:211 ℃ 时间:2020-05-19 00:57:43
解答
(x-y+9)(x+y-9),
=[x-(y-9)][x+(y-9)],
=x2-(y-9)2
=x2-(y2-18y+81),
=x2-y2+18y-81.
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