Question

9(a+b)的二次方-(a-b)的二次方

Answer 1

=[3(a+b)]²-(a-b)²

=[3(a+b)+(a-b)][3(a+b)-(a-b)]

=(3a+3b+a-b)(3a+3b-a+b)

=(4a+2b)(2a+4b)

=4(2a+b)(a+2b)