原式=[3(2a+3b)]²-[2(3a-2b)]²
=[3(2a+3b)+2(3a-2b)][(3(2a+3b)-2(3a-2b)]
=(6a+9b+6a-4b)(6a+9b-6a+4b)
=(12a+5b)×13b
=13b(12a+5b)