Specific question on lcm and gcd of rings.












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I can't prove this statement:



Let $a_1,a_2,...,a_n$ and $b_1,b_2,...,b_n$ be non zero elements of an integral domain $R$ such that $a_1b_1=a_2b_2=cdots=a_nb_n=x$



If $gcd(ra_1,ra_2,...,ra_n)$ exists for all $0neq rin R$, then $lcm(b_1,b_2,...,b_n)$ also exists and satisfies $$gcd(a_1,a_2,...,a_n)lcm(b_1b_2,...,b_n)=x$$



Any hints?



I use the following lemma:



Let $a_1,a_2,...,a_n$ and $r$ be nonzero elements of an integral domain $R$.



$1)$ if $lcm(a_1,a_2,..a_n)$ exists, then $lcm(ra_1,ra_2,...,ra_n)$ also exists and $$lcm(ra_1,ra_2,...ra_n)=rlcm(a_1,a_2,...,a_n)$$



$2)$ if $gcd(ra_1,ra_2,...,ra_n)$ exists, then $gcd(a_1,a_2,...a_n)$ also exists and $$gcd(ra_1,ra_2,...,ra_n)=rgcd(a_1,a_2,...,a_n).$$



My attemp:
We suppose that $gcd(ra_1,ra_2,...,ra_n)$ exists, therefore $a:=gcd(a_1,a_2,...,a_n)$ exists for the lemma, and therefore $a| a_i$ for each $i$. Since $x=a_ib_i$ we obtain that $ab_i |x$. We easily can show that $x=lcm(ab_1,ab_2,...,ab_n)$ but i don't know how procede then.



Any hints?










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    0












    $begingroup$


    I can't prove this statement:



    Let $a_1,a_2,...,a_n$ and $b_1,b_2,...,b_n$ be non zero elements of an integral domain $R$ such that $a_1b_1=a_2b_2=cdots=a_nb_n=x$



    If $gcd(ra_1,ra_2,...,ra_n)$ exists for all $0neq rin R$, then $lcm(b_1,b_2,...,b_n)$ also exists and satisfies $$gcd(a_1,a_2,...,a_n)lcm(b_1b_2,...,b_n)=x$$



    Any hints?



    I use the following lemma:



    Let $a_1,a_2,...,a_n$ and $r$ be nonzero elements of an integral domain $R$.



    $1)$ if $lcm(a_1,a_2,..a_n)$ exists, then $lcm(ra_1,ra_2,...,ra_n)$ also exists and $$lcm(ra_1,ra_2,...ra_n)=rlcm(a_1,a_2,...,a_n)$$



    $2)$ if $gcd(ra_1,ra_2,...,ra_n)$ exists, then $gcd(a_1,a_2,...a_n)$ also exists and $$gcd(ra_1,ra_2,...,ra_n)=rgcd(a_1,a_2,...,a_n).$$



    My attemp:
    We suppose that $gcd(ra_1,ra_2,...,ra_n)$ exists, therefore $a:=gcd(a_1,a_2,...,a_n)$ exists for the lemma, and therefore $a| a_i$ for each $i$. Since $x=a_ib_i$ we obtain that $ab_i |x$. We easily can show that $x=lcm(ab_1,ab_2,...,ab_n)$ but i don't know how procede then.



    Any hints?










    share|cite|improve this question











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      0












      0








      0





      $begingroup$


      I can't prove this statement:



      Let $a_1,a_2,...,a_n$ and $b_1,b_2,...,b_n$ be non zero elements of an integral domain $R$ such that $a_1b_1=a_2b_2=cdots=a_nb_n=x$



      If $gcd(ra_1,ra_2,...,ra_n)$ exists for all $0neq rin R$, then $lcm(b_1,b_2,...,b_n)$ also exists and satisfies $$gcd(a_1,a_2,...,a_n)lcm(b_1b_2,...,b_n)=x$$



      Any hints?



      I use the following lemma:



      Let $a_1,a_2,...,a_n$ and $r$ be nonzero elements of an integral domain $R$.



      $1)$ if $lcm(a_1,a_2,..a_n)$ exists, then $lcm(ra_1,ra_2,...,ra_n)$ also exists and $$lcm(ra_1,ra_2,...ra_n)=rlcm(a_1,a_2,...,a_n)$$



      $2)$ if $gcd(ra_1,ra_2,...,ra_n)$ exists, then $gcd(a_1,a_2,...a_n)$ also exists and $$gcd(ra_1,ra_2,...,ra_n)=rgcd(a_1,a_2,...,a_n).$$



      My attemp:
      We suppose that $gcd(ra_1,ra_2,...,ra_n)$ exists, therefore $a:=gcd(a_1,a_2,...,a_n)$ exists for the lemma, and therefore $a| a_i$ for each $i$. Since $x=a_ib_i$ we obtain that $ab_i |x$. We easily can show that $x=lcm(ab_1,ab_2,...,ab_n)$ but i don't know how procede then.



      Any hints?










      share|cite|improve this question











      $endgroup$




      I can't prove this statement:



      Let $a_1,a_2,...,a_n$ and $b_1,b_2,...,b_n$ be non zero elements of an integral domain $R$ such that $a_1b_1=a_2b_2=cdots=a_nb_n=x$



      If $gcd(ra_1,ra_2,...,ra_n)$ exists for all $0neq rin R$, then $lcm(b_1,b_2,...,b_n)$ also exists and satisfies $$gcd(a_1,a_2,...,a_n)lcm(b_1b_2,...,b_n)=x$$



      Any hints?



      I use the following lemma:



      Let $a_1,a_2,...,a_n$ and $r$ be nonzero elements of an integral domain $R$.



      $1)$ if $lcm(a_1,a_2,..a_n)$ exists, then $lcm(ra_1,ra_2,...,ra_n)$ also exists and $$lcm(ra_1,ra_2,...ra_n)=rlcm(a_1,a_2,...,a_n)$$



      $2)$ if $gcd(ra_1,ra_2,...,ra_n)$ exists, then $gcd(a_1,a_2,...a_n)$ also exists and $$gcd(ra_1,ra_2,...,ra_n)=rgcd(a_1,a_2,...,a_n).$$



      My attemp:
      We suppose that $gcd(ra_1,ra_2,...,ra_n)$ exists, therefore $a:=gcd(a_1,a_2,...,a_n)$ exists for the lemma, and therefore $a| a_i$ for each $i$. Since $x=a_ib_i$ we obtain that $ab_i |x$. We easily can show that $x=lcm(ab_1,ab_2,...,ab_n)$ but i don't know how procede then.



      Any hints?







      abstract-algebra ring-theory greatest-common-divisor least-common-multiple






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      edited Dec 10 '18 at 19:36







      Domenico Vuono

















      asked Dec 10 '18 at 17:19









      Domenico VuonoDomenico Vuono

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