How to prove that if x^n*y=y*x^n, then x and y commute

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Discussion Overview

The discussion revolves around the conditions under which the equation x^n*y = y*x^n implies that the elements x and y of a group commute. Participants explore the implications of this relationship, considering both general and specific cases of n.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant notes that if x and y commute, then the equation y*x^n = x^n*y holds true.
  • Another participant challenges the necessity of the original statement, questioning whether it holds when x and y do not commute, particularly if x^n equals the identity element E for some n.
  • A participant points out the ambiguity in the interpretation of n, suggesting that it could either be a specific integer or a general positive integer.
  • There is a discussion about the implications of n being a general integer, with one participant asserting that if n is general, the case n=1 must be considered, which complicates the argument.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the equation and whether it necessarily leads to the conclusion that x and y commute. The discussion remains unresolved with multiple competing perspectives on the nature of n and its impact on the argument.

Contextual Notes

There are limitations regarding the assumptions about n, including whether it is treated as a specific integer or a general positive integer, which affects the validity of the claims made.

landor
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Let x and y be elements of a group.

I can see that it works the other way, i.e. if x and y commute, then y*x^n = x^n*y...
 
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Write down the equation that represents x and y commuting, and then the equation you have beneath it. How can you make the second one become the first?
 
Is it necessarily true?
What about the case where x and y don't commute, but xn=E for some specific n?
 
Sorry, I'm used to seeing n representing a general positive integer so I assumed that was the case here as well.
 
Well, the problem with that is n either has a specific value or is a general integer...if it's a general integer, then it's trivial to consider the case n=1. So I'm assuming that's not what is meant.
 
Thanks.
 

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