1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    Hello tim656. Welcome to PF !

    Think about some subset of the complex numbers.

    What are the multiples of the imaginary unit, i ?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook