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(3a-b+2c)(3a+b-2c)+(b+2c)平方
人气:300 ℃ 时间:2020-05-12 11:38:26
解答
(3a-b+2c)(3a+b-2c)+(b+2c)^2
=(3a-(b-2c))(3a+b-2c)+(b+2c)^2
=(3a)^2-(b-2c)^2+(b+2c)^2
=9a^2-8bc
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