If gcd(a,b) = 1, can any integer be written as a linear combination of a,b?

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I am thinking about this in the context of the two water jugs problem. I know that a jug of capacity n can be filled if gcd(a,b) | n. Does this have the corollary that any integer can be written as a linear combination of a and b if gcd(a,b) = 1.










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  • Yes, that is right
    – DonAntonio
    34 mins ago










  • If $gcd(a,b) = 1$ then there are $c,d $ such that $ac+bd = 1$ and hence if $p$ is an integer we can write $p = (cp)a + (dp)b$.
    – copper.hat
    32 mins ago














up vote
1
down vote

favorite












I am thinking about this in the context of the two water jugs problem. I know that a jug of capacity n can be filled if gcd(a,b) | n. Does this have the corollary that any integer can be written as a linear combination of a and b if gcd(a,b) = 1.










share|cite|improve this question







New contributor




taurus is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.



















  • Yes, that is right
    – DonAntonio
    34 mins ago










  • If $gcd(a,b) = 1$ then there are $c,d $ such that $ac+bd = 1$ and hence if $p$ is an integer we can write $p = (cp)a + (dp)b$.
    – copper.hat
    32 mins ago












up vote
1
down vote

favorite









up vote
1
down vote

favorite











I am thinking about this in the context of the two water jugs problem. I know that a jug of capacity n can be filled if gcd(a,b) | n. Does this have the corollary that any integer can be written as a linear combination of a and b if gcd(a,b) = 1.










share|cite|improve this question







New contributor




taurus is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











I am thinking about this in the context of the two water jugs problem. I know that a jug of capacity n can be filled if gcd(a,b) | n. Does this have the corollary that any integer can be written as a linear combination of a and b if gcd(a,b) = 1.







combinatorics number-theory elementary-number-theory puzzle






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  • Yes, that is right
    – DonAntonio
    34 mins ago










  • If $gcd(a,b) = 1$ then there are $c,d $ such that $ac+bd = 1$ and hence if $p$ is an integer we can write $p = (cp)a + (dp)b$.
    – copper.hat
    32 mins ago
















  • Yes, that is right
    – DonAntonio
    34 mins ago










  • If $gcd(a,b) = 1$ then there are $c,d $ such that $ac+bd = 1$ and hence if $p$ is an integer we can write $p = (cp)a + (dp)b$.
    – copper.hat
    32 mins ago















Yes, that is right
– DonAntonio
34 mins ago




Yes, that is right
– DonAntonio
34 mins ago












If $gcd(a,b) = 1$ then there are $c,d $ such that $ac+bd = 1$ and hence if $p$ is an integer we can write $p = (cp)a + (dp)b$.
– copper.hat
32 mins ago




If $gcd(a,b) = 1$ then there are $c,d $ such that $ac+bd = 1$ and hence if $p$ is an integer we can write $p = (cp)a + (dp)b$.
– copper.hat
32 mins ago










2 Answers
2






active

oldest

votes

















up vote
4
down vote



accepted










Yes that's a consequence of Bézout's identity which can be proved by Euclidean algorithm and which states that



$$forall a,bin mathbbZquad gcd(a,b)=1 iff exists x,yin mathbbZquad ax+by=1$$



from which we obtain that



$$acdot nx+bcdot ny=n$$






share|cite|improve this answer






















  • @copper.hat Thanks for the editing, the fact is that I've also encountered that as "Bezout's theorem" but "Bezout's identity" seems to be the official name.
    – gimusi
    28 mins ago










  • Bézout's theorem is usually interpreted in the context of algebraic geometry,
    – copper.hat
    27 mins ago










  • @copper.hat Indeed I'm completely unaware about algebraic geometry :)
    – gimusi
    25 mins ago










  • Thank you very much!
    – taurus
    23 mins ago

















up vote
0
down vote













In general, if $d=gcd(a,b)$, then any integer of the form $nd$ for some integer $n$ can be expressed as a linear combination of $a$ and $b$. This is because we can write $a=da_1$ and $b=db_1$ for integers $a_1,b_1$ so that $gcd(a_1,b_1)=1$. By the euclidean algorithm this leads us to the fact that there exists $k_1,k_2$ such that
$$1=k_1a_1+k_2b_1$$
for all $a_1,b_1$. Multiplying both sides of the equation by $nd$, we get
$$nd=nk_1(da_1)+nk_2(db_1)=nk_1a+nk_2b$$
Which gives us a way to find anything of the form $nd$ as a linear combination of $a,b$.






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    2 Answers
    2






    active

    oldest

    votes








    2 Answers
    2






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes








    up vote
    4
    down vote



    accepted










    Yes that's a consequence of Bézout's identity which can be proved by Euclidean algorithm and which states that



    $$forall a,bin mathbbZquad gcd(a,b)=1 iff exists x,yin mathbbZquad ax+by=1$$



    from which we obtain that



    $$acdot nx+bcdot ny=n$$






    share|cite|improve this answer






















    • @copper.hat Thanks for the editing, the fact is that I've also encountered that as "Bezout's theorem" but "Bezout's identity" seems to be the official name.
      – gimusi
      28 mins ago










    • Bézout's theorem is usually interpreted in the context of algebraic geometry,
      – copper.hat
      27 mins ago










    • @copper.hat Indeed I'm completely unaware about algebraic geometry :)
      – gimusi
      25 mins ago










    • Thank you very much!
      – taurus
      23 mins ago














    up vote
    4
    down vote



    accepted










    Yes that's a consequence of Bézout's identity which can be proved by Euclidean algorithm and which states that



    $$forall a,bin mathbbZquad gcd(a,b)=1 iff exists x,yin mathbbZquad ax+by=1$$



    from which we obtain that



    $$acdot nx+bcdot ny=n$$






    share|cite|improve this answer






















    • @copper.hat Thanks for the editing, the fact is that I've also encountered that as "Bezout's theorem" but "Bezout's identity" seems to be the official name.
      – gimusi
      28 mins ago










    • Bézout's theorem is usually interpreted in the context of algebraic geometry,
      – copper.hat
      27 mins ago










    • @copper.hat Indeed I'm completely unaware about algebraic geometry :)
      – gimusi
      25 mins ago










    • Thank you very much!
      – taurus
      23 mins ago












    up vote
    4
    down vote



    accepted







    up vote
    4
    down vote



    accepted






    Yes that's a consequence of Bézout's identity which can be proved by Euclidean algorithm and which states that



    $$forall a,bin mathbbZquad gcd(a,b)=1 iff exists x,yin mathbbZquad ax+by=1$$



    from which we obtain that



    $$acdot nx+bcdot ny=n$$






    share|cite|improve this answer














    Yes that's a consequence of Bézout's identity which can be proved by Euclidean algorithm and which states that



    $$forall a,bin mathbbZquad gcd(a,b)=1 iff exists x,yin mathbbZquad ax+by=1$$



    from which we obtain that



    $$acdot nx+bcdot ny=n$$







    share|cite|improve this answer














    share|cite|improve this answer



    share|cite|improve this answer








    edited 30 mins ago

























    answered 32 mins ago









    gimusi

    78.1k73889




    78.1k73889











    • @copper.hat Thanks for the editing, the fact is that I've also encountered that as "Bezout's theorem" but "Bezout's identity" seems to be the official name.
      – gimusi
      28 mins ago










    • Bézout's theorem is usually interpreted in the context of algebraic geometry,
      – copper.hat
      27 mins ago










    • @copper.hat Indeed I'm completely unaware about algebraic geometry :)
      – gimusi
      25 mins ago










    • Thank you very much!
      – taurus
      23 mins ago
















    • @copper.hat Thanks for the editing, the fact is that I've also encountered that as "Bezout's theorem" but "Bezout's identity" seems to be the official name.
      – gimusi
      28 mins ago










    • Bézout's theorem is usually interpreted in the context of algebraic geometry,
      – copper.hat
      27 mins ago










    • @copper.hat Indeed I'm completely unaware about algebraic geometry :)
      – gimusi
      25 mins ago










    • Thank you very much!
      – taurus
      23 mins ago















    @copper.hat Thanks for the editing, the fact is that I've also encountered that as "Bezout's theorem" but "Bezout's identity" seems to be the official name.
    – gimusi
    28 mins ago




    @copper.hat Thanks for the editing, the fact is that I've also encountered that as "Bezout's theorem" but "Bezout's identity" seems to be the official name.
    – gimusi
    28 mins ago












    Bézout's theorem is usually interpreted in the context of algebraic geometry,
    – copper.hat
    27 mins ago




    Bézout's theorem is usually interpreted in the context of algebraic geometry,
    – copper.hat
    27 mins ago












    @copper.hat Indeed I'm completely unaware about algebraic geometry :)
    – gimusi
    25 mins ago




    @copper.hat Indeed I'm completely unaware about algebraic geometry :)
    – gimusi
    25 mins ago












    Thank you very much!
    – taurus
    23 mins ago




    Thank you very much!
    – taurus
    23 mins ago










    up vote
    0
    down vote













    In general, if $d=gcd(a,b)$, then any integer of the form $nd$ for some integer $n$ can be expressed as a linear combination of $a$ and $b$. This is because we can write $a=da_1$ and $b=db_1$ for integers $a_1,b_1$ so that $gcd(a_1,b_1)=1$. By the euclidean algorithm this leads us to the fact that there exists $k_1,k_2$ such that
    $$1=k_1a_1+k_2b_1$$
    for all $a_1,b_1$. Multiplying both sides of the equation by $nd$, we get
    $$nd=nk_1(da_1)+nk_2(db_1)=nk_1a+nk_2b$$
    Which gives us a way to find anything of the form $nd$ as a linear combination of $a,b$.






    share|cite|improve this answer
























      up vote
      0
      down vote













      In general, if $d=gcd(a,b)$, then any integer of the form $nd$ for some integer $n$ can be expressed as a linear combination of $a$ and $b$. This is because we can write $a=da_1$ and $b=db_1$ for integers $a_1,b_1$ so that $gcd(a_1,b_1)=1$. By the euclidean algorithm this leads us to the fact that there exists $k_1,k_2$ such that
      $$1=k_1a_1+k_2b_1$$
      for all $a_1,b_1$. Multiplying both sides of the equation by $nd$, we get
      $$nd=nk_1(da_1)+nk_2(db_1)=nk_1a+nk_2b$$
      Which gives us a way to find anything of the form $nd$ as a linear combination of $a,b$.






      share|cite|improve this answer






















        up vote
        0
        down vote










        up vote
        0
        down vote









        In general, if $d=gcd(a,b)$, then any integer of the form $nd$ for some integer $n$ can be expressed as a linear combination of $a$ and $b$. This is because we can write $a=da_1$ and $b=db_1$ for integers $a_1,b_1$ so that $gcd(a_1,b_1)=1$. By the euclidean algorithm this leads us to the fact that there exists $k_1,k_2$ such that
        $$1=k_1a_1+k_2b_1$$
        for all $a_1,b_1$. Multiplying both sides of the equation by $nd$, we get
        $$nd=nk_1(da_1)+nk_2(db_1)=nk_1a+nk_2b$$
        Which gives us a way to find anything of the form $nd$ as a linear combination of $a,b$.






        share|cite|improve this answer












        In general, if $d=gcd(a,b)$, then any integer of the form $nd$ for some integer $n$ can be expressed as a linear combination of $a$ and $b$. This is because we can write $a=da_1$ and $b=db_1$ for integers $a_1,b_1$ so that $gcd(a_1,b_1)=1$. By the euclidean algorithm this leads us to the fact that there exists $k_1,k_2$ such that
        $$1=k_1a_1+k_2b_1$$
        for all $a_1,b_1$. Multiplying both sides of the equation by $nd$, we get
        $$nd=nk_1(da_1)+nk_2(db_1)=nk_1a+nk_2b$$
        Which gives us a way to find anything of the form $nd$ as a linear combination of $a,b$.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered 19 mins ago









        user496634

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