则 的值是( )
| ··· | -3 | -2 | -1 | 0 | 2 | 3 | 4 | 5 | ··· |
| ··· | -0.5 | -1 | -2 | -5 | 7 | 4 | 3 | 2.5 | ··· |
①;
②.