If p is prime, prove the group (Zp*,x) has exactly one element of order 2.

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Discussion Overview

The discussion revolves around proving that the group (Zp*, x) has exactly one element of order 2, where p is a prime number and (Zp*, x) represents the multiplicative group of integers modulo p. The scope includes theoretical exploration and mathematical reasoning related to group theory.

Discussion Character

  • Exploratory, Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant seeks assistance in proving that (Zp*, x) has exactly one element of order 2.
  • Another participant suggests that identifying which element has order 2 may simplify the task and recommends clarifying the condition for an element to have order 2.
  • A different participant mentions that the group \mathbb{Z}_p^* is cyclic, implying that this property may be relevant to the proof.
  • Another suggestion involves considering the polynomial X^2-1 in \mathbb{Z}_p[X] and prompts participants to think about its roots as a potential avenue for exploration.

Areas of Agreement / Disagreement

The discussion does not appear to reach a consensus, as participants offer different approaches and insights without resolving the main question.

Contextual Notes

Participants have not explicitly defined the conditions for an element to have order 2, nor have they fully explored the implications of \mathbb{Z}_p^* being cyclic or the roots of the polynomial X^2-1.

ae1709
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Hi. I need to: prove the group (Zp*,x) has exactly one element of order 2. Here, p is prime and (Zp*,x) is the set {1, 2,..., p-1} under multiplication modulo p. Any help would be much appreciated!
 
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I think the easier half is: which element has order two?

It might help if you write down the condition of what it means to have order 2
 
Something that might help you is knowing that \mathbb{Z}_p^* is cyclic. Do you know this already??
 
If you do not know the previous. Then you might want to think about the polynomial X^2-1 in \mathbb{Z}_p[X]. What do you know about its roots??
 

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