Taking the Homomorphism of a Subgroup [duplicate] The Next CEO of Stack OverflowShowing the...

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Taking the Homomorphism of a Subgroup [duplicate]



The Next CEO of Stack OverflowShowing the image of a subgroup is a subgroup.Image of subgroup and Kernel of homomorphism form subgroupsDoes the image $f(H) subseteq G'$ for $H subseteq G$?Is every quotient of a finite abelian group $G$ isomorphic to some subgroup of $G$?How do I show a mapping is a homomorphism?What would the cosets of this subgroup be?Normality of subgroup of image of homomorphismProving that a homomorphism is abeliannumber of homomorphism from $G$ to $G' times G' times cdots times G'$ ($k$ terms)Group Homomorphism Question from Completed MidtermFor homomorphism $phi: Gto H$, if $G_{1}leq G$ and $|G_{1}|=n$, then $|phi(G_{1})|$ divides $n$.If $H$ and $K$ are normal subgroups of $G$ and $Hbigcap K = {e}$, prove that $G$ is isomorphic to a subgroup of $G/H times G/K$How to find homomorphism of direct product?












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This question already has an answer here:




  • Showing the image of a subgroup is a subgroup. [duplicate]

    1 answer




Let $phi : G rightarrow G'$ be a homomorphism. We want to show that $H leq G$ implies that $phi(H) leq G'$.



This is one of those problems that seems obviously true to the intuition, yet I'm having a devil of a time trying to prove it formally. A sketch of my efforts so far:



Let us define the codomain of $H$ under $phi$ to be $H'$, and $h'$ to be an arbitrary element of $H'$ such that $phi(h)=h'$ (for $h in H$).



To achieve the desired result, we have to show that $h' in G'$.



What I want to say is that, since $H leq G$, then every $h$ in $H$ is also in $G$, and thus clearly $h' in G'$. Is it that simple, or am I begging the question?










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marked as duplicate by Dietrich Burde group-theory
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Mar 16 at 17:48


This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.


















  • $begingroup$
    If $a, b in H$ then $phi(ab^{-1}) in H'.$ Now use the fact that you have a homomorphism.
    $endgroup$
    – Sean Roberson
    Mar 16 at 17:47










  • $begingroup$
    You have shown that $H’$ is a $textit{subset}$ of $G’$, not that it is a $textit{subgroup}$, which is what the question is asking. So to show that it’s a subgroup, what do you have to show about $H’$? (You will need to use the properties of homomorphisms here.)
    $endgroup$
    – Alex Sanger
    Mar 16 at 17:52


















0












$begingroup$



This question already has an answer here:




  • Showing the image of a subgroup is a subgroup. [duplicate]

    1 answer




Let $phi : G rightarrow G'$ be a homomorphism. We want to show that $H leq G$ implies that $phi(H) leq G'$.



This is one of those problems that seems obviously true to the intuition, yet I'm having a devil of a time trying to prove it formally. A sketch of my efforts so far:



Let us define the codomain of $H$ under $phi$ to be $H'$, and $h'$ to be an arbitrary element of $H'$ such that $phi(h)=h'$ (for $h in H$).



To achieve the desired result, we have to show that $h' in G'$.



What I want to say is that, since $H leq G$, then every $h$ in $H$ is also in $G$, and thus clearly $h' in G'$. Is it that simple, or am I begging the question?










share|cite|improve this question









$endgroup$



marked as duplicate by Dietrich Burde group-theory
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Mar 16 at 17:48


This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.


















  • $begingroup$
    If $a, b in H$ then $phi(ab^{-1}) in H'.$ Now use the fact that you have a homomorphism.
    $endgroup$
    – Sean Roberson
    Mar 16 at 17:47










  • $begingroup$
    You have shown that $H’$ is a $textit{subset}$ of $G’$, not that it is a $textit{subgroup}$, which is what the question is asking. So to show that it’s a subgroup, what do you have to show about $H’$? (You will need to use the properties of homomorphisms here.)
    $endgroup$
    – Alex Sanger
    Mar 16 at 17:52
















0












0








0





$begingroup$



This question already has an answer here:




  • Showing the image of a subgroup is a subgroup. [duplicate]

    1 answer




Let $phi : G rightarrow G'$ be a homomorphism. We want to show that $H leq G$ implies that $phi(H) leq G'$.



This is one of those problems that seems obviously true to the intuition, yet I'm having a devil of a time trying to prove it formally. A sketch of my efforts so far:



Let us define the codomain of $H$ under $phi$ to be $H'$, and $h'$ to be an arbitrary element of $H'$ such that $phi(h)=h'$ (for $h in H$).



To achieve the desired result, we have to show that $h' in G'$.



What I want to say is that, since $H leq G$, then every $h$ in $H$ is also in $G$, and thus clearly $h' in G'$. Is it that simple, or am I begging the question?










share|cite|improve this question









$endgroup$





This question already has an answer here:




  • Showing the image of a subgroup is a subgroup. [duplicate]

    1 answer




Let $phi : G rightarrow G'$ be a homomorphism. We want to show that $H leq G$ implies that $phi(H) leq G'$.



This is one of those problems that seems obviously true to the intuition, yet I'm having a devil of a time trying to prove it formally. A sketch of my efforts so far:



Let us define the codomain of $H$ under $phi$ to be $H'$, and $h'$ to be an arbitrary element of $H'$ such that $phi(h)=h'$ (for $h in H$).



To achieve the desired result, we have to show that $h' in G'$.



What I want to say is that, since $H leq G$, then every $h$ in $H$ is also in $G$, and thus clearly $h' in G'$. Is it that simple, or am I begging the question?





This question already has an answer here:




  • Showing the image of a subgroup is a subgroup. [duplicate]

    1 answer








group-theory group-homomorphism






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Mar 16 at 17:37









JustSomeGuy716JustSomeGuy716

94




94




marked as duplicate by Dietrich Burde group-theory
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Mar 16 at 17:48


This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.









marked as duplicate by Dietrich Burde group-theory
Users with the  group-theory badge can single-handedly close group-theory questions as duplicates and reopen them as needed.

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Mar 16 at 17:48


This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.














  • $begingroup$
    If $a, b in H$ then $phi(ab^{-1}) in H'.$ Now use the fact that you have a homomorphism.
    $endgroup$
    – Sean Roberson
    Mar 16 at 17:47










  • $begingroup$
    You have shown that $H’$ is a $textit{subset}$ of $G’$, not that it is a $textit{subgroup}$, which is what the question is asking. So to show that it’s a subgroup, what do you have to show about $H’$? (You will need to use the properties of homomorphisms here.)
    $endgroup$
    – Alex Sanger
    Mar 16 at 17:52




















  • $begingroup$
    If $a, b in H$ then $phi(ab^{-1}) in H'.$ Now use the fact that you have a homomorphism.
    $endgroup$
    – Sean Roberson
    Mar 16 at 17:47










  • $begingroup$
    You have shown that $H’$ is a $textit{subset}$ of $G’$, not that it is a $textit{subgroup}$, which is what the question is asking. So to show that it’s a subgroup, what do you have to show about $H’$? (You will need to use the properties of homomorphisms here.)
    $endgroup$
    – Alex Sanger
    Mar 16 at 17:52


















$begingroup$
If $a, b in H$ then $phi(ab^{-1}) in H'.$ Now use the fact that you have a homomorphism.
$endgroup$
– Sean Roberson
Mar 16 at 17:47




$begingroup$
If $a, b in H$ then $phi(ab^{-1}) in H'.$ Now use the fact that you have a homomorphism.
$endgroup$
– Sean Roberson
Mar 16 at 17:47












$begingroup$
You have shown that $H’$ is a $textit{subset}$ of $G’$, not that it is a $textit{subgroup}$, which is what the question is asking. So to show that it’s a subgroup, what do you have to show about $H’$? (You will need to use the properties of homomorphisms here.)
$endgroup$
– Alex Sanger
Mar 16 at 17:52






$begingroup$
You have shown that $H’$ is a $textit{subset}$ of $G’$, not that it is a $textit{subgroup}$, which is what the question is asking. So to show that it’s a subgroup, what do you have to show about $H’$? (You will need to use the properties of homomorphisms here.)
$endgroup$
– Alex Sanger
Mar 16 at 17:52












1 Answer
1






active

oldest

votes


















0












$begingroup$

Hint: You have to show that, for $h_1,h_2$ we have $phi(h_1)phi(h_2)in G'$ and $phi(h_1)^{-1}in G'$. Then $phi(H)$ is a subgroup of $G'$.



Reference: This duplicate:



Image of subgroup and Kernel of homomorphism form subgroups






share|cite|improve this answer









$endgroup$




















    1 Answer
    1






    active

    oldest

    votes








    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    0












    $begingroup$

    Hint: You have to show that, for $h_1,h_2$ we have $phi(h_1)phi(h_2)in G'$ and $phi(h_1)^{-1}in G'$. Then $phi(H)$ is a subgroup of $G'$.



    Reference: This duplicate:



    Image of subgroup and Kernel of homomorphism form subgroups






    share|cite|improve this answer









    $endgroup$


















      0












      $begingroup$

      Hint: You have to show that, for $h_1,h_2$ we have $phi(h_1)phi(h_2)in G'$ and $phi(h_1)^{-1}in G'$. Then $phi(H)$ is a subgroup of $G'$.



      Reference: This duplicate:



      Image of subgroup and Kernel of homomorphism form subgroups






      share|cite|improve this answer









      $endgroup$
















        0












        0








        0





        $begingroup$

        Hint: You have to show that, for $h_1,h_2$ we have $phi(h_1)phi(h_2)in G'$ and $phi(h_1)^{-1}in G'$. Then $phi(H)$ is a subgroup of $G'$.



        Reference: This duplicate:



        Image of subgroup and Kernel of homomorphism form subgroups






        share|cite|improve this answer









        $endgroup$



        Hint: You have to show that, for $h_1,h_2$ we have $phi(h_1)phi(h_2)in G'$ and $phi(h_1)^{-1}in G'$. Then $phi(H)$ is a subgroup of $G'$.



        Reference: This duplicate:



        Image of subgroup and Kernel of homomorphism form subgroups







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Mar 16 at 17:46









        Dietrich BurdeDietrich Burde

        81.6k648106




        81.6k648106















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