| 12−2(m+3) |
| (m+3)(m−3) |
| −2(m−3) |
| (m+3)(m−3) |
| 2 |
| (m+3) |
（2）原式=
| x(x+9) |
| x(x+3) |
| (x+3)(x−3) |
| (x+3)2 |
| (x+9) |
| (x+3) |
| (x−3) |
| (x+3) |
| 2x+6 |
| x+3 |
| 12 |
| m2−9 |
| 2 |
| m−3 |
| x2+9x |
| x2+3x |
| x2−9 |
| x2+6x+9 |
| 12−2(m+3) |
| (m+3)(m−3) |
| −2(m−3) |
| (m+3)(m−3) |
| 2 |
| (m+3) |
| x(x+9) |
| x(x+3) |
| (x+3)(x−3) |
| (x+3)2 |
| (x+9) |
| (x+3) |
| (x−3) |
| (x+3) |
| 2x+6 |
| x+3 |