Exponent of a finite group $G$











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Let $G$ be a finite group. The exponent of $G$, $exp(G)$ is defined as the minimal positive integer $m$ such that $x^m=1$ for all $x in G$.
prove:



$a)$ if $G$ is abelian then $exp(G)= max{text{ord}(x):x in G}$



$b)$ if $G$ is not abelian the previous statement may fail.










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  • Is my solution correct?
    – mathnoob
    Nov 18 at 2:30















up vote
1
down vote

favorite












Let $G$ be a finite group. The exponent of $G$, $exp(G)$ is defined as the minimal positive integer $m$ such that $x^m=1$ for all $x in G$.
prove:



$a)$ if $G$ is abelian then $exp(G)= max{text{ord}(x):x in G}$



$b)$ if $G$ is not abelian the previous statement may fail.










share|cite|improve this question
























  • Is my solution correct?
    – mathnoob
    Nov 18 at 2:30













up vote
1
down vote

favorite









up vote
1
down vote

favorite











Let $G$ be a finite group. The exponent of $G$, $exp(G)$ is defined as the minimal positive integer $m$ such that $x^m=1$ for all $x in G$.
prove:



$a)$ if $G$ is abelian then $exp(G)= max{text{ord}(x):x in G}$



$b)$ if $G$ is not abelian the previous statement may fail.










share|cite|improve this question















Let $G$ be a finite group. The exponent of $G$, $exp(G)$ is defined as the minimal positive integer $m$ such that $x^m=1$ for all $x in G$.
prove:



$a)$ if $G$ is abelian then $exp(G)= max{text{ord}(x):x in G}$



$b)$ if $G$ is not abelian the previous statement may fail.







finite-groups






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edited Nov 18 at 2:25









hanszimmer

195




195










asked Nov 18 at 2:10









mathnoob

1,133116




1,133116












  • Is my solution correct?
    – mathnoob
    Nov 18 at 2:30


















  • Is my solution correct?
    – mathnoob
    Nov 18 at 2:30
















Is my solution correct?
– mathnoob
Nov 18 at 2:30




Is my solution correct?
– mathnoob
Nov 18 at 2:30










1 Answer
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Here is my attempt for



$a)$
$G$ is finite abelian, so $G$ is direct sums of $k$ $mathbb{Z}/p_i mathbb{Z}$'s for some $k in mathbb{N}$ and $p_i|p_{i+1}$ for all $i$. Hence element with highest order is $(1,...,1)$ with order $lcm(p_1,...,p_k)=p_k$ which is the highest order of any element in $G$ which is $exp(G)$.



$b)$ $S_3$ is a counterexample.






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    down vote













    Here is my attempt for



    $a)$
    $G$ is finite abelian, so $G$ is direct sums of $k$ $mathbb{Z}/p_i mathbb{Z}$'s for some $k in mathbb{N}$ and $p_i|p_{i+1}$ for all $i$. Hence element with highest order is $(1,...,1)$ with order $lcm(p_1,...,p_k)=p_k$ which is the highest order of any element in $G$ which is $exp(G)$.



    $b)$ $S_3$ is a counterexample.






    share|cite|improve this answer

























      up vote
      0
      down vote













      Here is my attempt for



      $a)$
      $G$ is finite abelian, so $G$ is direct sums of $k$ $mathbb{Z}/p_i mathbb{Z}$'s for some $k in mathbb{N}$ and $p_i|p_{i+1}$ for all $i$. Hence element with highest order is $(1,...,1)$ with order $lcm(p_1,...,p_k)=p_k$ which is the highest order of any element in $G$ which is $exp(G)$.



      $b)$ $S_3$ is a counterexample.






      share|cite|improve this answer























        up vote
        0
        down vote










        up vote
        0
        down vote









        Here is my attempt for



        $a)$
        $G$ is finite abelian, so $G$ is direct sums of $k$ $mathbb{Z}/p_i mathbb{Z}$'s for some $k in mathbb{N}$ and $p_i|p_{i+1}$ for all $i$. Hence element with highest order is $(1,...,1)$ with order $lcm(p_1,...,p_k)=p_k$ which is the highest order of any element in $G$ which is $exp(G)$.



        $b)$ $S_3$ is a counterexample.






        share|cite|improve this answer












        Here is my attempt for



        $a)$
        $G$ is finite abelian, so $G$ is direct sums of $k$ $mathbb{Z}/p_i mathbb{Z}$'s for some $k in mathbb{N}$ and $p_i|p_{i+1}$ for all $i$. Hence element with highest order is $(1,...,1)$ with order $lcm(p_1,...,p_k)=p_k$ which is the highest order of any element in $G$ which is $exp(G)$.



        $b)$ $S_3$ is a counterexample.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Nov 18 at 2:10









        mathnoob

        1,133116




        1,133116






























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