答：（1）（a²-b²）/（a+b)=(a-b)(a+b) /(a+b)=a-b（2）（x²-4x-5）/(x+1)=(x-5)(x+1)/(x+1)=x-5（3）（ax²-2ax-3a)/(x-3) =a(x²-2x-3)/(x-3)=a(x-3)(x+1)/(x-3)=a(x+1)（4）[（x+y）²...