1)【(a+1)/(a²-a)+4/(1-a²)】÷（a-1)
=[a﹙a+1﹚﹙a-1﹚-4﹙a+1﹚﹙a-1﹚]÷(a-1)
=a﹙a+1﹚-4﹙a+1﹚
=a²＋a-4a-4
=a²-3a-4
2）【a-(a²-b²+1)/a】÷【（b-1）/a】×【1/(a+b)】
=[﹙a²-a²＋b²-1﹚／a]×[a／﹙b-1﹚]×[1／﹙a＋b﹚]
=[﹙b＋1﹚﹙b－1﹚﹚／a]×[a／﹙b-1﹚]×[1／﹙a＋b﹚]
＝﹙b+1﹚／﹙a+b﹚
3）（2x²-6x）/(x²-9)-(x+3)/(3-x)-(2x+6)/(x²+6x+9)
=[2x﹙x-3﹚／﹙x-3﹚﹙x+3﹚]＋﹙x+3﹚／﹙x－3﹚－2﹙x+3﹚／﹙x＋3﹚³
=2x／﹙x+3﹚－2／﹙x+3﹚＋﹙x+3﹚／﹙x－3﹚
=﹙2x-2﹚／﹙x+3﹚＋﹙x+3﹚／﹙x－3﹚
=﹙2x-2﹚﹙x-3﹚+﹙x+3﹚²／﹙x+3﹚﹙x－3﹚
＝﹙3x²-2x+15﹚／﹙x+3﹚﹙x－3﹚