If G solvable and S a subgroup, then S is solvable [duplicate]












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  • Subgroups of finite solvable groups. Solvable?

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Let $G$ be a solvable group, and $S$ a subgroup. Prove that $S$ is solvable.



Let $G$ be solvable. Then there exists a sequence of subgroups $$ { e}triangleleft H_rtriangleleft H_{r-1}cdots triangleleft H_1 triangleleft H_0=G $$ such that $H_{i+1}triangleleft H_i$ for $i=0, ...r-1,$ and $H_i/H_{i+1}$ is abelian. If $S=H_i$, where $H_i$ is as above for $ineq r$, then it is trivial. So we need to assume that $Sneq H_i.$ Let $N_S$ be the normalizer of $S$ in $G$. We know that $Striangleleft N_S$ and $N_S$ is a subgroup of $G.$ Here I am stuck.



Can somebody propose a solution or give me some hint. Thanks.










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marked as duplicate by Jyrki Lahtonen abstract-algebra
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Dec 27 '18 at 17:30


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    This question already has an answer here:




    • Subgroups of finite solvable groups. Solvable?

      2 answers




    Let $G$ be a solvable group, and $S$ a subgroup. Prove that $S$ is solvable.



    Let $G$ be solvable. Then there exists a sequence of subgroups $$ { e}triangleleft H_rtriangleleft H_{r-1}cdots triangleleft H_1 triangleleft H_0=G $$ such that $H_{i+1}triangleleft H_i$ for $i=0, ...r-1,$ and $H_i/H_{i+1}$ is abelian. If $S=H_i$, where $H_i$ is as above for $ineq r$, then it is trivial. So we need to assume that $Sneq H_i.$ Let $N_S$ be the normalizer of $S$ in $G$. We know that $Striangleleft N_S$ and $N_S$ is a subgroup of $G.$ Here I am stuck.



    Can somebody propose a solution or give me some hint. Thanks.










    share|cite|improve this question















    marked as duplicate by Jyrki Lahtonen abstract-algebra
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    Dec 27 '18 at 17:30


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      This question already has an answer here:




      • Subgroups of finite solvable groups. Solvable?

        2 answers




      Let $G$ be a solvable group, and $S$ a subgroup. Prove that $S$ is solvable.



      Let $G$ be solvable. Then there exists a sequence of subgroups $$ { e}triangleleft H_rtriangleleft H_{r-1}cdots triangleleft H_1 triangleleft H_0=G $$ such that $H_{i+1}triangleleft H_i$ for $i=0, ...r-1,$ and $H_i/H_{i+1}$ is abelian. If $S=H_i$, where $H_i$ is as above for $ineq r$, then it is trivial. So we need to assume that $Sneq H_i.$ Let $N_S$ be the normalizer of $S$ in $G$. We know that $Striangleleft N_S$ and $N_S$ is a subgroup of $G.$ Here I am stuck.



      Can somebody propose a solution or give me some hint. Thanks.










      share|cite|improve this question
















      This question already has an answer here:




      • Subgroups of finite solvable groups. Solvable?

        2 answers




      Let $G$ be a solvable group, and $S$ a subgroup. Prove that $S$ is solvable.



      Let $G$ be solvable. Then there exists a sequence of subgroups $$ { e}triangleleft H_rtriangleleft H_{r-1}cdots triangleleft H_1 triangleleft H_0=G $$ such that $H_{i+1}triangleleft H_i$ for $i=0, ...r-1,$ and $H_i/H_{i+1}$ is abelian. If $S=H_i$, where $H_i$ is as above for $ineq r$, then it is trivial. So we need to assume that $Sneq H_i.$ Let $N_S$ be the normalizer of $S$ in $G$. We know that $Striangleleft N_S$ and $N_S$ is a subgroup of $G.$ Here I am stuck.



      Can somebody propose a solution or give me some hint. Thanks.





      This question already has an answer here:




      • Subgroups of finite solvable groups. Solvable?

        2 answers








      abstract-algebra group-theory






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      edited Dec 27 '18 at 17:28

























      asked Dec 27 '18 at 17:22









      user249018

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      393127




      marked as duplicate by Jyrki Lahtonen abstract-algebra
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      Dec 27 '18 at 17:30


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      marked as duplicate by Jyrki Lahtonen abstract-algebra
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          suppose that $G$ is resolvable and that ${H_i}_0^n$ is a series of composition of $G$ such that $H_{i+1}/H_i$ is cyclic $0leq ileq n-1$. Let $T$ be a subgroup $G$ either. For each $i$ we can define $T_i=Tcap H_i$ so that $T_i$ is a subgroup of $T$. Avoiding the duplication of those $T_i$ that are repeated, that is, those that comply with $Tcap H_i=Tcap H_{i+1}$ we can form a series of $T$ composition.
          $${e}=T_0’leq cdots T_m’=T$$
          Then $T_{i+1}’/T_i’=(Tcap H_{i+1})/(Tcap H_i)$ is a cyclic group. Therefore $T$ es resolvable.






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            suppose that $G$ is resolvable and that ${H_i}_0^n$ is a series of composition of $G$ such that $H_{i+1}/H_i$ is cyclic $0leq ileq n-1$. Let $T$ be a subgroup $G$ either. For each $i$ we can define $T_i=Tcap H_i$ so that $T_i$ is a subgroup of $T$. Avoiding the duplication of those $T_i$ that are repeated, that is, those that comply with $Tcap H_i=Tcap H_{i+1}$ we can form a series of $T$ composition.
            $${e}=T_0’leq cdots T_m’=T$$
            Then $T_{i+1}’/T_i’=(Tcap H_{i+1})/(Tcap H_i)$ is a cyclic group. Therefore $T$ es resolvable.






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              suppose that $G$ is resolvable and that ${H_i}_0^n$ is a series of composition of $G$ such that $H_{i+1}/H_i$ is cyclic $0leq ileq n-1$. Let $T$ be a subgroup $G$ either. For each $i$ we can define $T_i=Tcap H_i$ so that $T_i$ is a subgroup of $T$. Avoiding the duplication of those $T_i$ that are repeated, that is, those that comply with $Tcap H_i=Tcap H_{i+1}$ we can form a series of $T$ composition.
              $${e}=T_0’leq cdots T_m’=T$$
              Then $T_{i+1}’/T_i’=(Tcap H_{i+1})/(Tcap H_i)$ is a cyclic group. Therefore $T$ es resolvable.






              share|cite|improve this answer
























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                suppose that $G$ is resolvable and that ${H_i}_0^n$ is a series of composition of $G$ such that $H_{i+1}/H_i$ is cyclic $0leq ileq n-1$. Let $T$ be a subgroup $G$ either. For each $i$ we can define $T_i=Tcap H_i$ so that $T_i$ is a subgroup of $T$. Avoiding the duplication of those $T_i$ that are repeated, that is, those that comply with $Tcap H_i=Tcap H_{i+1}$ we can form a series of $T$ composition.
                $${e}=T_0’leq cdots T_m’=T$$
                Then $T_{i+1}’/T_i’=(Tcap H_{i+1})/(Tcap H_i)$ is a cyclic group. Therefore $T$ es resolvable.






                share|cite|improve this answer












                suppose that $G$ is resolvable and that ${H_i}_0^n$ is a series of composition of $G$ such that $H_{i+1}/H_i$ is cyclic $0leq ileq n-1$. Let $T$ be a subgroup $G$ either. For each $i$ we can define $T_i=Tcap H_i$ so that $T_i$ is a subgroup of $T$. Avoiding the duplication of those $T_i$ that are repeated, that is, those that comply with $Tcap H_i=Tcap H_{i+1}$ we can form a series of $T$ composition.
                $${e}=T_0’leq cdots T_m’=T$$
                Then $T_{i+1}’/T_i’=(Tcap H_{i+1})/(Tcap H_i)$ is a cyclic group. Therefore $T$ es resolvable.







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                answered Dec 27 '18 at 17:47









                Julio Trujillo Gonzalez

                856




                856















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