设G={[1] [2] [3] [4] [5] [6]} G上的二元运算×7如表5-36所示.(G ×7)是循环群吗?若是 请找出它的生成元.
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设G={[1],[2],[3],[4],[5],[6]},G上的二元运算×7如表5-36所示.(G,×7)是循环群吗?若是,请找出它的生成元.
| 表5-36 | ||||||
| ×7 | [1] | [2] | [3] | [4] | [5] | [6] |
| [1] | [1] | [2] | [3] | [4] | [5] | [6] |
| [2] | [2] | [4] | [6] | [1] | [3] | [5] |
| [3] | [3] | [6] | [2] | [5] | [1] | [4] |
| [4] | [4] | [1] | [5] | [2] | [6] | [3] |
| [5] | [5] | [3] | [1] | [6] | [4] | [2] |
| [6] | [6] | [5] | [4] | [3] | [2] | [1] |
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显然,(G,×7)是封闭的,具有结合律.[1]为它的单位元,[2]与[4]、[3]与[5]互为逆元,[6]的逆元是[6].故(G,×7)是群.
通过观察可知:
[3]2=[3]×7[3]=[2],[3]3=[3]×7[3]2=[3]×7[2]=[6],
[3]4=[3]×7[3]3=[3]×7[6]=[4],[3]5=[3]×7[3]4=[3]×7[4]=[5],
[3]6=[3]×7[3]5=[3]5×7[5]=[1],
所以,[3]是群(G,×7)的生成元.
