9a(a-4)∧2-6a∧2(4-a)-3(4-a)
=9a(a-4)²+6a²(a-4)+3(a-4)
=[9a(a-4)+6a²+3](a-4)
=(9a²-36a+6a²+3)(a-4)
=(15a²-36a+3)(a-4)
=3(5a²-12a+1)(a-4)