Results 1 to 2 of 2

Math Help - Commutative Rings and units

  1. #1
    Newbie
    Joined
    Feb 2009
    Posts
    21

    Commutative Rings and units

    Let R = { m+n*\sqrt{2} |  m,n \in Z}

    Q: Show that 1+2\sqrt{2} has infinite order in R^x

    From previous part of the Problem:
    m+n*\sqrt{2} is a unit in R if and only if m^2-2n^2= \pm{1}

    I'm a little confused by this since according to the above theorem 1+2\sqrt{2} is not a unit

    What am I missing? Is it actually a unit?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Newbie
    Joined
    Feb 2009
    Posts
    21
    disregard this thread. Its a typo in the book
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Rings- a^2 = a then R must be commutative
    Posted in the Advanced Algebra Forum
    Replies: 6
    Last Post: February 8th 2011, 04:59 PM
  2. Binomial Theorem and Commutative Rings
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: September 26th 2010, 08:19 AM
  3. Commutative Rings and Fields
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: November 30th 2009, 07:04 PM
  4. Prime Ideals of Commutative Rings
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: April 14th 2009, 07:27 PM
  5. rings commutative with 1 - what does this mean?
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: February 28th 2009, 03:12 AM

Search Tags


/mathhelpforum @mathhelpforum