[(a+3)分之（a²-a-6）]²乘以[(a²+a-6)分之（a-3)]的负二次方=[(a-3)(a+2)/(a+3)×(a+3)(a-2)/(a-3)]²=[(a+2)(a-2)]²=(a²-4)²=a的4次方-8a²+16