| 10x−10−x |
| 10x+10−x |
| 102x−1 |
| 102x+1 |
f（x）=
| 10−x−10x |
| 10−x+10x |
| 102x−1 |
| 102x+1 |
∴f（x）是奇函数
（2）f(x)＝
| 102x−1 |
| 102x+1 |
则f(x1) −f(x2) ＝
| 102x1−1 |
| 102x1+1 |
| 102x2−1 |
| 102x2+1 |
| 2(102x1−102x2) |
| (102x1+1)(102x2+1) |
| 2(100x1−100x2) |
| (102x1+1)(102x2+1) |
因为x1＜x2，所以100x1＜100x2，所以f（x1）-f（x2）＜0，即f（x1）＜f（x2），
∴f（x）为增函数．