Finding subgroups of Factor/ Quotient Groups

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Homework Help Overview

The problem involves identifying and describing all the subgroups of the groups Z/9Z and Z/3Z x Z/3Z, including determining the number of such subgroups.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster expresses uncertainty about how to begin addressing the problem. Some participants attempt to identify elements and their orders in Z/9Z, suggesting the existence of certain subgroups. Others provide information about the structure of Z/3Z x Z/3Z and its non-cyclic nature.

Discussion Status

Participants are sharing their attempts and seeking validation of their reasoning. There is an ongoing exploration of subgroup structures, with some guidance being offered regarding the elements of Z/9Z and the nature of Z/3Z x Z/3Z.

Contextual Notes

There appears to be a lack of clarity regarding the definitions and properties of the groups involved, as well as the specific requirements for describing the subgroups.

porroadventum
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Homework Statement



Describe all the subgroups of Z/9Z. How many are there? Describe all the subgroups of Z/3ZxZ/3Z. How many are there?


The Attempt at a Solution



I don't even know where to start with this question. If someone could just point me in the right direction that would be great.

Thank you.
 
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I have made an attempt, if someone could let me know if it is correct or not, that would be much appreciated!

The elements of Z/9Z are {0,1,2,3,4,5,6,7,8} with operation modulo9.

The elements (1,2,4,5,7,8} have order 9 and generate the whole group.
{0,3,6} has order 3.

Therefore there are two subgroups.
 
porroadventum said:
I have made an attempt, if someone could let me know if it is correct or not, that would be much appreciated!

The elements of Z/9Z are {0,1,2,3,4,5,6,7,8} with operation modulo9.

The elements (1,2,4,5,7,8} have order 9 and generate the whole group.
{0,3,6} has order 3.

Therefore there are two subgroups.

{0} is also a subgroup.
 
It looks like you're good for ##Z/9Z##.

##Z/3Z \times Z/3Z## is {(0,0),(0,1),(0,2),(1,0),(1,1),(1,2),(2,0),(2,1),(2,2)} - which is not cyclic.
 

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