| a+b |
| a-b |
| 2b+1 |
| b-a |
| a-b-1 |
| a-b |
| a-b-1 |
| a-b |
| 1 |
| x-2 |
| 1 |
| x2-5x+6 |
| 1 |
| x-3 |
| 1 |
| x-3 |
| 1 |
| f |
| 1 |
| u |
| 1 |
| v |
| fu |
| u-f |
| fu |
| u-f |
| 1 |
| x2-1 |
| x |
| 1-x2 |
| 1 |
| x+1 |
| 1 |
| x+1 |
| a |
| a-b |
| b |
| a-b |
| a |
| a-b |
| b |
| b-a |
| x2 |
| x2-y2 |
| y2 |
| x2-y2 |
| wx |
| wx-y |
| y |
| y-wx |
| w |
| xw-1 |
| 1 |
| 1+x |
| 3a2 |
| 4b |
| 16b |
| 9a |
| x2 |
| x-1 |
| 1 |
| 1-x |
| 3x |
| x-4y |
| x+y |
| 4y-x |
| 7y |
| x-4y |
| a2+b2 |
| a2-b2 |
| a-b |
| a+b |
| 2ab |
| (a-b)(a+b) |
| a2-2a+1 |
| a-1 |
| 3 |
| a |
| 1 |
| a |