Help with Abstract Algebra: Show ac=b, da=b w/Hint

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Discussion Overview

The discussion revolves around a problem in abstract algebra concerning the existence of elements \(c\) and \(d\) in a group \(G\) such that \(ac = b\) and \(da = b\) for given elements \(a\) and \(b\) in \(G\). Participants explore various approaches to proving this statement, including the use of group properties and inverses.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant requests help with the problem and expresses uncertainty about how to solve it.
  • Another participant asks what the original poster has tried, prompting further elaboration on their approach.
  • The original poster mentions attempting to use matrices but finds it unhelpful.
  • A participant suggests that the properties of group elements, specifically the existence of inverses and the closure under multiplication, are key to solving the problem.
  • One participant proposes a proof for \(ac = b\) using the inverse of \(a\), stating that \(a(a^{-1}b) = b\) and discusses the uniqueness of solutions through left cancellation.
  • Another participant suggests defining \(d\) as \(ba^{-1}\) to address the equation \(da = b\), indicating a similar approach to the first part of the problem.
  • Further discussion includes the application of cancellation properties in groups to justify the steps taken in the proofs.

Areas of Agreement / Disagreement

Participants appear to agree on the general approach of using group properties to define \(c\) and \(d\), but there is no consensus on the completeness or correctness of the proofs presented. Some participants express uncertainty about the sufficiency of their arguments.

Contextual Notes

Participants have not fully resolved the mathematical steps required to demonstrate the existence of \(c\) and \(d\) in all cases, and there are unresolved questions about the uniqueness of these elements based on the cancellation properties discussed.

patelnjigar
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Please I need your help for that qustion and how do slove that qustion's problem. can you help me for slove for that? Pleasee

Let G be any group, and let a, b ∈ G. Show that there are c, d ∈ G such that ac = b and da = b. Hint: you have to give an explicit definition for c and d in terms of a and b.
 
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what have you tried?
 
I have tried set up matrices for that but not work. I don't know how to slove for this problem...


Let G be any group, and let a, b ∈ G. Show that there are c, d ∈ G such that ac = b and da = b. Hint: you have to give an explicit definition for c and d in terms of a and b.
 
Matrices?? All you need is:
(i) if x is in G, then so is its inverse
(ii) if x,y are in G, then so is xy
 
i m tried work on this..

GIVE a, b ∈ G
SHOW c, d ∈ G ?

ac=b da=b

ac=b ---> proof: a (a^(-1)b)=b (IS THAT RIGHT? I THINK SO AND THAT'S RIGHT)

da=b ---> proof: ?
 
if i want to say about ac=b

proof: a (a^(-1)b)=b
uniqueness
if ac=ad=b
then c=d (left Cancellation)

How do I slove for da=b?? I need for that..
 
Same idea: let d = ba^(-1).
 
Same idea: let d = ba^(-1). ?? I seem that not enough

ac=b
a (a^(-1)b)=b, if ac=ad=b, then c=d (left cancellation).. I m sure that's right.



da=b
d=ba(a^(-1)), if ad=ac=b, then d=c (right cancellation) is that right?
 

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