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Homework Help: Finite and infinite group

  1. Sep 15, 2012 #1
    what is an infinite group that has exactly two elements with order 4?

    i let G be an infinite group for all R_5 ( multiplication modulo 5) within this interval [1,7)
    so i got |2|=|3|=4.

    i'm not sure this is the right answer but i couldn't think of anything else at a moment. help please.
     
  2. jcsd
  3. Sep 16, 2012 #2

    SammyS

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    Hello tim656. Welcome to PF !

    Think about some subset of the complex numbers.

    What are the multiples of the imaginary unit, i ?
     
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