| 4 |
| 2 |
| 1 |
| 3 |
| a |
| 3 |
| a2 |
| 1 |
| a3 |
| a+b |
| c |
| b+c |
| a |
| c+a |
| b |
| (a+b)(b+c)(c+a) |
| abc |
| 2 |
| x+3 |
| 2 |
| 3-x |
| 2x+18 |
| x2-9 |
| 1 |
| a |
| 1 |
| b |
| 1 |
| a+b |
| a |
| b |
| b |
| a |
| 5 |
| 5 |
| a-1 |
| 1 |
| ab |
| 1 |
| (a+1)(b+1) |
| 1 |
| (a+1990)(b+1990) |
| 1991 |
| 1992 |
| 1991 |
| 1992 |
| 1 |
| ab |
| 1 |
| (a+1)(b+1) |
| 1 |
| (a+2)(b+2) |
| 1 |
| (a+2007)(b+2007) |
| 2008 |
| 2009 |
| 2008 |
| 2009 |
| x |
| x2-x+1 |
| x2 |
| x4+x2+1 |
| 49 |
| 15 |
| 49 |
| 15 |
| 1 |
| x-1 |
| x |
| x2-1 |
(x+
| ||||
(x+
|
| b |
| a |
| c |
| b |
| a+b |
| b+c |
| 3 |
| 8 |
| 3 |
| 8 |