(a-2b-3c)(a+2b+3c)
=a^2-(4b^2+9c^2+6bc) =a^2-4b^2-9c^2-6bc
(a-2b-3c)(a+2b+3c) =[a-(2b+3c)]*[a+(2b+3c)] =a^2-(2b+3c)^2 =a^2-4b^2-12bc-9c^2
(a-2b-3c)(a+2b+3c) =[a-(2b+3c)][a+(2b+3c)] =a^2-(2b+3c)^2 =a^2-4b^2-12bc-9c^2
答:(a-2b+3c)(a+2b-3c)= [a-(2b-3c)][a+(2b-3c)]= a^2-(2b-3c)^2= a^2-4b^2+12bc-9c^2详情>>
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