| 2 |
| x−1 |
| x+1 |
| x−1 |
| 1−x |
| x−1 |
（2）原式=
| x+3 |
| 3−x |
| (x+3)(x−3) |
| (x+3)2 |
| x−3 |
| x+3 |
| x+3 |
| x−3 |
| (x−3)2−(x+3)2 |
| (x+3)(x−3) |
| 12x |
| x2−9 |
（3）原式=
| a+2 |
| 1 |
| 4 |
| a−2 |
| (a+2)(a−2)+4 |
| a−2 |
| a2 |
| a−2 |
| 2 |
| x−1 |
| x+1 |
| 1−x |
| x+3 |
| 3−x |
| x2−9 |
| x2+6x+9 |
| 4 |
| 2−a |
| 2 |
| x−1 |
| x+1 |
| x−1 |
| 1−x |
| x−1 |
| x+3 |
| 3−x |
| (x+3)(x−3) |
| (x+3)2 |
| x−3 |
| x+3 |
| x+3 |
| x−3 |
| (x−3)2−(x+3)2 |
| (x+3)(x−3) |
| 12x |
| x2−9 |
| a+2 |
| 1 |
| 4 |
| a−2 |
| (a+2)(a−2)+4 |
| a−2 |
| a2 |
| a−2 |