(1)(-2M+N)²
=4M²-4MN+N²
(2)(-2M-N)²
=4M²+4MN+N²
(3) (2A+B)²-(2A-B)²
=﹙2A+B+2A-B﹚﹙2A+B-2A+B﹚
=4A×2B
=8AB