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问题: 1. (a+b-c)(a-b+c)-(a-b-c)(a+b+c)

1. (a+b-c)(a-b+c)-(a-b-c)(a+b+c)
要详细步骤

解答:

=[a+(b-c)][a-(b-c)]-[a-(b+c)][a+(b+c)]
=a^2-(b-c)^2-a^2+(b+c)^2
=b^2-2bc+c^2+b^2+2bc+c^2
=2b^2+2c^2