问题 填空题

(a-2b+3c)(a+2b-3c)=______.

答案

(a-2b+3c)(a+2b-3c),

=[a-(2b-3c)][a+(2b-3c)],

=a2-(2b-3c)2

=a2-(4b2-12bc+9c2),

=a2-4b2+12bc-9c2

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