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Math Help - Prove that Un is a group with respect to multiplication.

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    Prove that Un is a group with respect to multiplication.

    For an integer n > 1, let G = Un, the group of units in Zn; that is, the set of all [a] in Zn that have multiplicative inverses. Prove that Un is a group with respect to multiplication.
    Last edited by MissMousey; May 2nd 2010 at 04:36 PM.
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    MHF Contributor Drexel28's Avatar
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    Quote Originally Posted by MissMousey View Post
    For an integer n > 1, let G = Un, the group of units in Zn; that is, the set of all [a] in Zn that have multiplicative inverses. Prove that Un is a group with respect to multiplication.
    I mean, what's the problem? Maybe the following will help you

    Theorem: The equation ax\equiv1\text{ mod }n is solvable precisely when (a,n)=1
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