﹙x²+3x﹚²-﹙2x+6﹚²
=﹙x²+3x-2x-6﹚﹙x²+3x+2x+6﹚
=﹙x²+x-6﹚﹙x²+5x+6﹚
=﹙x-2﹚﹙x+3﹚﹙x+2﹚﹙x+3﹚
=﹙x-2﹚﹙x+2﹚﹙x+3﹚²