| 1 |
| x(x+1) |
| 1 |
| (x+1)(x+2) |
| 1 |
| (x+2)(x+3) |
| 1 |
| (x+1998)(x+1999) |
=
| 1 |
| x |
| 1 |
| x+1 |
| 1 |
| x+1 |
| 1 |
| x+2 |
| 1 |
| x+2 |
| 1 |
| x+3 |
| 1 |
| x+1998 |
| 1 |
| x+1999 |
=
| 1 |
| x |
| 1 |
| x+1999 |
当x=1时，原式=1-
| 1 |
| 1+1999 |
| 1999 |
| 2000 |
| 1 |
| x(x+1) |
| 1 |
| (x+1)(x+2) |
| 1 |
| (x+2)(x+3) |
| 1 |
| (x+1998)(x+1999) |
| 1 |
| x(x+1) |
| 1 |
| (x+1)(x+2) |
| 1 |
| (x+2)(x+3) |
| 1 |
| (x+1998)(x+1999) |
| 1 |
| x |
| 1 |
| x+1 |
| 1 |
| x+1 |
| 1 |
| x+2 |
| 1 |
| x+2 |
| 1 |
| x+3 |
| 1 |
| x+1998 |
| 1 |
| x+1999 |
| 1 |
| x |
| 1 |
| x+1999 |
| 1 |
| 1+1999 |
| 1999 |
| 2000 |