解
原式
=(a²+2ab²+b²-4ab)(a²-2ab+b²+4ab)-(a²-b²)²
=(a-b)²(a+b)²-(a²-b²)²
=[(a-b)(a+b)]²-(a²-b²)²
=(a²-b²)²-(a²-b²)²
=0