1 |
1−2 |
1 |
1+1 |
1 |
2 |
1 | ||
1−
|
即A中其他所有元素为-1,
1 |
2 |
(2)若3∈A,则
1 |
1−3 |
1 |
2 |
1 | ||
1+
|
2 |
3 |
1 | ||
1−
|
即A中其他所有元素−
1 |
2 |
2 |
3 |
(3)A中只有三个元素a,
1 |
1−a |
a−1 |
a |
证明:a∈A,则
1 |
1−a |
1 |
1−a |
则
1 | ||
1−
|
a−1 |
a |
a−1 |
a |
进而
1 | ||
1−
|
∵a≠
1 |
1−a |
1 |
1−a |
∴
1 |
1−a |
a−1 |
a |
∴A中只有3个元素a,
1 |
1−a |
a−1 |
a |
1 |
1−a |
1 |
1−2 |
1 |
1+1 |
1 |
2 |
1 | ||
1−
|
1 |
2 |
1 |
1−3 |
1 |
2 |
1 | ||
1+
|
2 |
3 |
1 | ||
1−
|
1 |
2 |
2 |
3 |
1 |
1−a |
a−1 |
a |
1 |
1−a |
1 |
1−a |
1 | ||
1−
|
a−1 |
a |
a−1 |
a |
1 | ||
1−
|
1 |
1−a |
1 |
1−a |
1 |
1−a |
a−1 |
a |
1 |
1−a |
a−1 |
a |