4ab(b-a)-(a-b)
=-4ab(a-b)-(a-b)³
=-(a-b)[4ab+(a-b)²]
=-（a-b）（4ab+a²-2ab+b²)
=-(a-b)(a²+2ab+b²)
=-(a-b)(a+b)²
=(b-a)(a+b)²