分式的：（1）a²-ab除ab-b² (2)x²-6x+9除以x²-9 （3）x

（1）a²-ab除ab-b² =a(a-b)/b(a-b)=a/b (2)x²-6x+9除以x²-9 =(x-3)²/(x+3)(x-3)=(x-3)/(x+3_ （3）x²-1除以x²+4x+4除（x+1）乘x+2除1-x=(x+1)(x-1)/(x+2)²×1/(x+1) ×(x+2)×[-1/(x-1)]=-1/(x+2)