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Re: Groups and Inverse order

Subject: Re: Groups and Inverse order
From: Paul Sperry
Date: Sat, 30 Jul 2005 20:55:03 GMT
Newsgroups: sci.math
In article <1122746633.067740.56910@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, ADH
<adoug48@xxxxxxxxxxx> wrote:

> Hi all,
> 
> I'm trying to solve the following problem on groups.
> a,) Let G be a group.  If a belongs to G, then the order of a is the
> same as the order of its inverse.

Note (g^n)^(-1) = (g^(-1))^n. Use induction if you need to prove it.

> b.) Let G be a group.  Let a,b belong to G.  Show that a and b have the
> same order if b=g^(-1)ag, for some element g belonging to G.

Note (g^(-1)ag)^n = g^(-1)a^ng. Use induction again if necessary. Also
note a = (g^(-1))^(-1)b(g^(-1).

> c.) Let G be a group. Show that ab and ba have the same order.

Use (b)

[...]

-- 
Paul Sperry
Columbia, SC (USA)

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