4(a-b)²-16(a-b)²
=4[(a-b)²-[2(a-b)]²]
=4(a-b+2a-2b)(a-b-2a+2b)
=4(3a-3b)(b-a)
=12(a-b)(b-a)
=-12(a-b)²
晕倒,亏我写这么多,是因式分解么