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2(x+y)(x-y)-(x+y)^2-(x-y)^2的完全平方公式是?
人气:336 ℃ 时间:2020-06-15 18:12:48
解答
=-[(x+y)²-2(x+y)(x-y)+(x-y)²]
=-[(x+y)-(x-y)]²
=(2y)²
=4y²
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