﹙1﹚25a²b²-10ab+1＝﹙5ab－1﹚²
﹙2﹚ 36a²-(a+9)²＝﹙6a－a－9﹚﹙6a＋a＋9﹚＝﹙5a－9﹚﹙7a＋9﹚
﹙3﹚16-8（x+y）+(x-y)²＝﹙4－x＋y﹚².