(Headbang)

Let G be a group, and . For any positive integer we define by

.

Now prove by induction:

If , then

*edit: Please, no spoilers. Just a nudge is all I need. Thanks.

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- October 23rd 2011, 05:39 AMVonNemo19prove by induction
(Headbang)

Let G be a group, and . For any positive integer we define by

.

Now prove by induction:

If , then

*edit: Please, no spoilers. Just a nudge is all I need. Thanks. - October 23rd 2011, 05:56 AMymarRe: prove by induction
So we know ab=ba. The base case n=1 is trivial. We need to carry out the inductive step. The inductive hypothesis is that . We need to prove that . How can we see here something that appears in the inductive hypothesis? When we see it, we can use ab=ba (more than once).

- October 23rd 2011, 08:43 AMDevenoRe: prove by induction
the trick is to see how you're going to get from the "n-step" to the "n+1-step".

let's see if we can prove from ab = ba.

do you see it coming...? we can just switch the middle pair.

.

now try it for , and see if you can generalize.....