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U(15) = {1, 2, 4, 7, 8, 11, 13, 14 }
 
U(15) = {1, 2, 4, 7, 8, 11, 13, 14 }
 
Then it goes on to say to find the order of element 7, so |7| = 4  
 
Then it goes on to say to find the order of element 7, so |7| = 4  
<math>7^1 = 7space  7^2 =4 space  7^3 = 13   7^4 = 1</math>
+
<math>7^1 = 7space  7^2 =4 space  7^3 = 13 space  7^4 = 1</math>

Revision as of 18:07, 15 September 2008

The problem says show that U(20) does not equal <k> for any k in U(20). [Hence U(20) is not cyclic.] I was trying to understand Example 1 from the Chapter 3 in the text book. where it discusses U(15). I am completely confused about what it is talking about:

U(15) = {1, 2, 4, 7, 8, 11, 13, 14 } Then it goes on to say to find the order of element 7, so |7| = 4 $ 7^1 = 7space 7^2 =4 space 7^3 = 13 space 7^4 = 1 $

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