Prove that if $m, n, dinmathbb{Z^+}$ and $d | m^2n+1, d | mn^2+1$ then $d | m^3+1, d | n^3+1$












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Prove that if $m, n, dinmathbb{Z^+}$ and $d | m^2n+1, d | mn^2+1$ then $d | m^3+1, d | n^3+1$




My attempt:



So I said that from this we can safely say that
$$m^2nequiv-1pmod{d}, mn^2equiv-1pmod{d}$$
This means that:
$$mn(m)equiv mn(n)pmod{d}$$
Now if $gcd(mn, d)=1$ then we will get that
$$mequiv{n}pmod{d}$$
Now in our original equation we will get
$$m^2n+1equiv0pmod{d}, mn^2+1equiv0pmod{d}$$
$$therefore m^3+1equiv0pmod{d}, n^3+1equiv0pmod{d}$$
But what if $gcd(mn,d)gt{1}$, what will I have to do? And is that even possible in the first place? Thank you in advance.










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$endgroup$

















    1












    $begingroup$



    Prove that if $m, n, dinmathbb{Z^+}$ and $d | m^2n+1, d | mn^2+1$ then $d | m^3+1, d | n^3+1$




    My attempt:



    So I said that from this we can safely say that
    $$m^2nequiv-1pmod{d}, mn^2equiv-1pmod{d}$$
    This means that:
    $$mn(m)equiv mn(n)pmod{d}$$
    Now if $gcd(mn, d)=1$ then we will get that
    $$mequiv{n}pmod{d}$$
    Now in our original equation we will get
    $$m^2n+1equiv0pmod{d}, mn^2+1equiv0pmod{d}$$
    $$therefore m^3+1equiv0pmod{d}, n^3+1equiv0pmod{d}$$
    But what if $gcd(mn,d)gt{1}$, what will I have to do? And is that even possible in the first place? Thank you in advance.










    share|cite|improve this question









    $endgroup$















      1












      1








      1





      $begingroup$



      Prove that if $m, n, dinmathbb{Z^+}$ and $d | m^2n+1, d | mn^2+1$ then $d | m^3+1, d | n^3+1$




      My attempt:



      So I said that from this we can safely say that
      $$m^2nequiv-1pmod{d}, mn^2equiv-1pmod{d}$$
      This means that:
      $$mn(m)equiv mn(n)pmod{d}$$
      Now if $gcd(mn, d)=1$ then we will get that
      $$mequiv{n}pmod{d}$$
      Now in our original equation we will get
      $$m^2n+1equiv0pmod{d}, mn^2+1equiv0pmod{d}$$
      $$therefore m^3+1equiv0pmod{d}, n^3+1equiv0pmod{d}$$
      But what if $gcd(mn,d)gt{1}$, what will I have to do? And is that even possible in the first place? Thank you in advance.










      share|cite|improve this question









      $endgroup$





      Prove that if $m, n, dinmathbb{Z^+}$ and $d | m^2n+1, d | mn^2+1$ then $d | m^3+1, d | n^3+1$




      My attempt:



      So I said that from this we can safely say that
      $$m^2nequiv-1pmod{d}, mn^2equiv-1pmod{d}$$
      This means that:
      $$mn(m)equiv mn(n)pmod{d}$$
      Now if $gcd(mn, d)=1$ then we will get that
      $$mequiv{n}pmod{d}$$
      Now in our original equation we will get
      $$m^2n+1equiv0pmod{d}, mn^2+1equiv0pmod{d}$$
      $$therefore m^3+1equiv0pmod{d}, n^3+1equiv0pmod{d}$$
      But what if $gcd(mn,d)gt{1}$, what will I have to do? And is that even possible in the first place? Thank you in advance.







      elementary-number-theory






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      asked Dec 15 '18 at 4:22









      user587054user587054

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          Let $p$ be any prime divisor of $d$, and let $k$ be the maximum natural number such that $p^k mid d$. Observe that: $p^k mid d mid mn(m-n)$, and $m^2n+1 = m^2(n-m+m)+1 = m^3+1 + (n-m)m^2$. This means that if $p^k nmid (n-m)implies p^k mid mnimplies p mid 1$, contradiction $p$ being a prime. Thus $p^k mid (n-m)$,and this means $p^k mid m^3+1$. Thus $d mid (m^3+1)$, and similarly $d mid (n^3+1)$. Note that if $p^r mid (n-m)$, and $p^s mid mn$ with $r+s = k$, then $p mid m^2n implies p mid 1$, contradiction $p$ being a prime.






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            $begingroup$

            Let $p$ be any prime divisor of $d$, and let $k$ be the maximum natural number such that $p^k mid d$. Observe that: $p^k mid d mid mn(m-n)$, and $m^2n+1 = m^2(n-m+m)+1 = m^3+1 + (n-m)m^2$. This means that if $p^k nmid (n-m)implies p^k mid mnimplies p mid 1$, contradiction $p$ being a prime. Thus $p^k mid (n-m)$,and this means $p^k mid m^3+1$. Thus $d mid (m^3+1)$, and similarly $d mid (n^3+1)$. Note that if $p^r mid (n-m)$, and $p^s mid mn$ with $r+s = k$, then $p mid m^2n implies p mid 1$, contradiction $p$ being a prime.






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              $begingroup$

              Let $p$ be any prime divisor of $d$, and let $k$ be the maximum natural number such that $p^k mid d$. Observe that: $p^k mid d mid mn(m-n)$, and $m^2n+1 = m^2(n-m+m)+1 = m^3+1 + (n-m)m^2$. This means that if $p^k nmid (n-m)implies p^k mid mnimplies p mid 1$, contradiction $p$ being a prime. Thus $p^k mid (n-m)$,and this means $p^k mid m^3+1$. Thus $d mid (m^3+1)$, and similarly $d mid (n^3+1)$. Note that if $p^r mid (n-m)$, and $p^s mid mn$ with $r+s = k$, then $p mid m^2n implies p mid 1$, contradiction $p$ being a prime.






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              $endgroup$
















                1












                1








                1





                $begingroup$

                Let $p$ be any prime divisor of $d$, and let $k$ be the maximum natural number such that $p^k mid d$. Observe that: $p^k mid d mid mn(m-n)$, and $m^2n+1 = m^2(n-m+m)+1 = m^3+1 + (n-m)m^2$. This means that if $p^k nmid (n-m)implies p^k mid mnimplies p mid 1$, contradiction $p$ being a prime. Thus $p^k mid (n-m)$,and this means $p^k mid m^3+1$. Thus $d mid (m^3+1)$, and similarly $d mid (n^3+1)$. Note that if $p^r mid (n-m)$, and $p^s mid mn$ with $r+s = k$, then $p mid m^2n implies p mid 1$, contradiction $p$ being a prime.






                share|cite|improve this answer









                $endgroup$



                Let $p$ be any prime divisor of $d$, and let $k$ be the maximum natural number such that $p^k mid d$. Observe that: $p^k mid d mid mn(m-n)$, and $m^2n+1 = m^2(n-m+m)+1 = m^3+1 + (n-m)m^2$. This means that if $p^k nmid (n-m)implies p^k mid mnimplies p mid 1$, contradiction $p$ being a prime. Thus $p^k mid (n-m)$,and this means $p^k mid m^3+1$. Thus $d mid (m^3+1)$, and similarly $d mid (n^3+1)$. Note that if $p^r mid (n-m)$, and $p^s mid mn$ with $r+s = k$, then $p mid m^2n implies p mid 1$, contradiction $p$ being a prime.







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                answered Dec 15 '18 at 5:10









                DeepSeaDeepSea

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                70.9k54487






























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