Show that G is an Abelian group

In summary, by choosing appropriate values for $c$, $d$, and $y$, it can be shown that $ab=ba$ for all $a$ and $b$ in the group $G$. Therefore, $G$ is an Abelian group.
  • #1
alexmahone
304
0
Let $G$ be a group such that for all $a$, $b$, $c$, $d$, and $y\in G$ if $ayb=cyd$ then $ab=cd$. Show that $G$ is an Abelian group.

HINTS ONLY as this is an assignment problem.
 
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  • #2
Consider $ayb=cyd$ when $y$ is the inverse of something.
 
  • #3
Evgeny.Makarov said:
Consider $ayb=cyd$ when $y$ is the inverse of something.

Even if I suppose $y=a^{-1}$ or $b^{-1}$ or $a^{-1}b^{-1}$, how do I know that $ayb=cyd$ has to be true?
 
  • #4
Alexmahone said:
Even if I suppose $y=a^{-1}$ or $b^{-1}$ or $a^{-1}b^{-1}$, how do I know that $ayb=cyd$ has to be true?
Given $a$ and $b$, you can make $ayb=cyd$ true by choosing $y$, $c$ and $d$ appropriately.

Another way to look at this is the following. You need to prove $ab=ba$ for all $a$ and $b$. Try to apply the implication that is given to you in post #1. For this you have to guess $y$ because it occurs only in the assumption and not the conclusion.
 
  • #5
I think I got it!

Take $c=b$ and $d=a$
Take $y=a^{-1}$

$ayb=aa^{-1}b=b$
$cyd=ba^{-1}a=b$
So, $ayb=cyd$
$\implies ab=cd$
i.e. $ab=ba$
So, $G$ is an Abelian group.
 
  • #6
Yes, that's correct.
 

Related to Show that G is an Abelian group

1. What is an Abelian group?

An Abelian group, also known as a commutative group, is a mathematical structure consisting of a set of elements and an operation that combines any two elements to produce a third element. The operation must be associative, have an identity element, and each element must have an inverse. In an Abelian group, the operation is also commutative, meaning that the order in which the elements are combined does not affect the result.

2. How do you show that a group G is Abelian?

To show that a group G is Abelian, you must demonstrate that the group satisfies the four defining properties of an Abelian group: associativity, identity element, inverses, and commutativity. This can be done by showing that the operation is associative, there exists an identity element, every element has an inverse, and the operation is commutative.

3. What is the significance of an Abelian group?

Abelian groups are important in mathematics because they have many useful properties and can be applied in various fields such as algebra, geometry, and number theory. They also serve as a foundation for more complex mathematical structures, such as rings and fields.

4. Can a non-Abelian group become an Abelian group?

No, a non-Abelian group cannot become an Abelian group. The defining properties of an Abelian group must be satisfied from the beginning, and a non-Abelian group lacks the commutativity property. However, some non-Abelian groups may have subgroups that are Abelian.

5. Can you provide an example of an Abelian group?

One example of an Abelian group is the group of integers under addition. The operation of addition is both associative and commutative, the identity element is 0, and every integer has an inverse (its negative). This group satisfies all the defining properties of an Abelian group.

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