| 1+x+1-x |
| (1-x)(1+x) |
| 2 |
| 1-x2 |
②原式=
| 2 |
| 1-x2 |
| 2 |
| 1+x2 |
| 2(1-x2+1+x2) |
| 1-x4 |
| 4 |
| 1-x4 |
③原式=
| 4 |
| 1-x4 |
| 4 |
| 1+x4 |
| 8 |
| 1+x8 |
| 16 |
| 1-x16 |
（2）①原式=
| p2+m2+n2 |
| mnp |
| (a-b)2+(b-c)2+(c-a)2 |
| (a-b)(b-c)(c-a) |
②若它们的值为0，则分子为0，根据几个非负数的和为0，则这几个非负数必须同时为0，此时分母等于0，分式无意义．所以这些分式的值不能等于0．
| 1 |
| 1-x |
| 1 |
| 1+x |
| 1 |
| 1-x |
| 1 |
| 1+x |
| 2 |
| 1+x2 |
| 1 |
| 1-x |
| 1 |
| 1+x |
| 2 |
| 1+x2 |
| 4 |
| 1+x4 |
| 8 |
| 1+x8 |
| p |
| mn |
| m |
| np |
| n |
| pm |
| (c-a) |
| (a-b)(b-c) |
| a-b |
| (b-c)(c-a) |
| b-c |
| (c-a)(a-b) |
| 1+x+1-x |
| (1-x)(1+x) |
| 2 |
| 1-x2 |
| 2 |
| 1-x2 |
| 2 |
| 1+x2 |
| 2(1-x2+1+x2) |
| 1-x4 |
| 4 |
| 1-x4 |
| 4 |
| 1-x4 |
| 4 |
| 1+x4 |
| 8 |
| 1+x8 |
| 16 |
| 1-x16 |
| p2+m2+n2 |
| mnp |
| (a-b)2+(b-c)2+(c-a)2 |
| (a-b)(b-c)(c-a) |