Can 2018 be written as a sum of two squares? If can, what is the expression?











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Can $2018$ be written as a sum of two squares?



If it can be, what are the numbers?




I know the first answer is it can be because $2018=2times1009$ and $1009equiv 1 pmod{4}$. But I cannot find the numbers.










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  • 1




    If all you care about is the numbers, then wolframalpha can help.
    – JMoravitz
    Dec 7 '17 at 4:18










  • By hit and trial, you can verify that $2018 = 13^2 + cdots$
    – Math Lover
    Dec 7 '17 at 4:21










  • For a small number like this, just make a column in a spreadsheet with $1$ to $45$ then =sqrt(2018-left^2) will make it easy to find. Just search by eye for the entries without decimals. They leap out.
    – Ross Millikan
    Dec 7 '17 at 4:21












  • See math.stackexchange.com/questions/1828694/…
    – lab bhattacharjee
    Dec 7 '17 at 4:41















up vote
0
down vote

favorite
2













Can $2018$ be written as a sum of two squares?



If it can be, what are the numbers?




I know the first answer is it can be because $2018=2times1009$ and $1009equiv 1 pmod{4}$. But I cannot find the numbers.










share|cite|improve this question




















  • 1




    If all you care about is the numbers, then wolframalpha can help.
    – JMoravitz
    Dec 7 '17 at 4:18










  • By hit and trial, you can verify that $2018 = 13^2 + cdots$
    – Math Lover
    Dec 7 '17 at 4:21










  • For a small number like this, just make a column in a spreadsheet with $1$ to $45$ then =sqrt(2018-left^2) will make it easy to find. Just search by eye for the entries without decimals. They leap out.
    – Ross Millikan
    Dec 7 '17 at 4:21












  • See math.stackexchange.com/questions/1828694/…
    – lab bhattacharjee
    Dec 7 '17 at 4:41













up vote
0
down vote

favorite
2









up vote
0
down vote

favorite
2






2






Can $2018$ be written as a sum of two squares?



If it can be, what are the numbers?




I know the first answer is it can be because $2018=2times1009$ and $1009equiv 1 pmod{4}$. But I cannot find the numbers.










share|cite|improve this question
















Can $2018$ be written as a sum of two squares?



If it can be, what are the numbers?




I know the first answer is it can be because $2018=2times1009$ and $1009equiv 1 pmod{4}$. But I cannot find the numbers.







elementary-number-theory






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share|cite|improve this question













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edited Dec 16 '17 at 17:39









amWhy

191k27223439




191k27223439










asked Dec 7 '17 at 4:15









Joe sae

65




65








  • 1




    If all you care about is the numbers, then wolframalpha can help.
    – JMoravitz
    Dec 7 '17 at 4:18










  • By hit and trial, you can verify that $2018 = 13^2 + cdots$
    – Math Lover
    Dec 7 '17 at 4:21










  • For a small number like this, just make a column in a spreadsheet with $1$ to $45$ then =sqrt(2018-left^2) will make it easy to find. Just search by eye for the entries without decimals. They leap out.
    – Ross Millikan
    Dec 7 '17 at 4:21












  • See math.stackexchange.com/questions/1828694/…
    – lab bhattacharjee
    Dec 7 '17 at 4:41














  • 1




    If all you care about is the numbers, then wolframalpha can help.
    – JMoravitz
    Dec 7 '17 at 4:18










  • By hit and trial, you can verify that $2018 = 13^2 + cdots$
    – Math Lover
    Dec 7 '17 at 4:21










  • For a small number like this, just make a column in a spreadsheet with $1$ to $45$ then =sqrt(2018-left^2) will make it easy to find. Just search by eye for the entries without decimals. They leap out.
    – Ross Millikan
    Dec 7 '17 at 4:21












  • See math.stackexchange.com/questions/1828694/…
    – lab bhattacharjee
    Dec 7 '17 at 4:41








1




1




If all you care about is the numbers, then wolframalpha can help.
– JMoravitz
Dec 7 '17 at 4:18




If all you care about is the numbers, then wolframalpha can help.
– JMoravitz
Dec 7 '17 at 4:18












By hit and trial, you can verify that $2018 = 13^2 + cdots$
– Math Lover
Dec 7 '17 at 4:21




By hit and trial, you can verify that $2018 = 13^2 + cdots$
– Math Lover
Dec 7 '17 at 4:21












For a small number like this, just make a column in a spreadsheet with $1$ to $45$ then =sqrt(2018-left^2) will make it easy to find. Just search by eye for the entries without decimals. They leap out.
– Ross Millikan
Dec 7 '17 at 4:21






For a small number like this, just make a column in a spreadsheet with $1$ to $45$ then =sqrt(2018-left^2) will make it easy to find. Just search by eye for the entries without decimals. They leap out.
– Ross Millikan
Dec 7 '17 at 4:21














See math.stackexchange.com/questions/1828694/…
– lab bhattacharjee
Dec 7 '17 at 4:41




See math.stackexchange.com/questions/1828694/…
– lab bhattacharjee
Dec 7 '17 at 4:41










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Yes, $2018 = 2times 1009$ (as prime factorization). Since $1009$ is an odd prime of the form $4k+1$, it can be written as a sum of two squares $1009 = a^2+b^2$. Together with $2 = 1^2 + 1^2$,
Brahmagupta–Fibonacci identity
$$(a^2+b^2)(c^2+d^2) = (ac-bd)^2 + (ad+bc)^2 = (ac+bd)^2 + (ad-bc)^2$$
tell us $2018 = (a+b)^2 + (a-b)^2$.



The task reduces to rewrite $1009$ as a sum of two squares. In addition to
seaching by brute force, one can use algorithms described in
answers of this question to determine $a,b$ efficiently. At the end, one find $$1009 = 28^2+15^2 quadimpliesquad 2018 = 43^2 + 13^2$$



A good reference of these sort of algorithms will be Henri Cohen's book
A course in Computation Algebraic Number Theory. Take a look at that if you need more details.






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    Yes, $2018 = 2times 1009$ (as prime factorization). Since $1009$ is an odd prime of the form $4k+1$, it can be written as a sum of two squares $1009 = a^2+b^2$. Together with $2 = 1^2 + 1^2$,
    Brahmagupta–Fibonacci identity
    $$(a^2+b^2)(c^2+d^2) = (ac-bd)^2 + (ad+bc)^2 = (ac+bd)^2 + (ad-bc)^2$$
    tell us $2018 = (a+b)^2 + (a-b)^2$.



    The task reduces to rewrite $1009$ as a sum of two squares. In addition to
    seaching by brute force, one can use algorithms described in
    answers of this question to determine $a,b$ efficiently. At the end, one find $$1009 = 28^2+15^2 quadimpliesquad 2018 = 43^2 + 13^2$$



    A good reference of these sort of algorithms will be Henri Cohen's book
    A course in Computation Algebraic Number Theory. Take a look at that if you need more details.






    share|cite|improve this answer



























      up vote
      5
      down vote













      Yes, $2018 = 2times 1009$ (as prime factorization). Since $1009$ is an odd prime of the form $4k+1$, it can be written as a sum of two squares $1009 = a^2+b^2$. Together with $2 = 1^2 + 1^2$,
      Brahmagupta–Fibonacci identity
      $$(a^2+b^2)(c^2+d^2) = (ac-bd)^2 + (ad+bc)^2 = (ac+bd)^2 + (ad-bc)^2$$
      tell us $2018 = (a+b)^2 + (a-b)^2$.



      The task reduces to rewrite $1009$ as a sum of two squares. In addition to
      seaching by brute force, one can use algorithms described in
      answers of this question to determine $a,b$ efficiently. At the end, one find $$1009 = 28^2+15^2 quadimpliesquad 2018 = 43^2 + 13^2$$



      A good reference of these sort of algorithms will be Henri Cohen's book
      A course in Computation Algebraic Number Theory. Take a look at that if you need more details.






      share|cite|improve this answer

























        up vote
        5
        down vote










        up vote
        5
        down vote









        Yes, $2018 = 2times 1009$ (as prime factorization). Since $1009$ is an odd prime of the form $4k+1$, it can be written as a sum of two squares $1009 = a^2+b^2$. Together with $2 = 1^2 + 1^2$,
        Brahmagupta–Fibonacci identity
        $$(a^2+b^2)(c^2+d^2) = (ac-bd)^2 + (ad+bc)^2 = (ac+bd)^2 + (ad-bc)^2$$
        tell us $2018 = (a+b)^2 + (a-b)^2$.



        The task reduces to rewrite $1009$ as a sum of two squares. In addition to
        seaching by brute force, one can use algorithms described in
        answers of this question to determine $a,b$ efficiently. At the end, one find $$1009 = 28^2+15^2 quadimpliesquad 2018 = 43^2 + 13^2$$



        A good reference of these sort of algorithms will be Henri Cohen's book
        A course in Computation Algebraic Number Theory. Take a look at that if you need more details.






        share|cite|improve this answer














        Yes, $2018 = 2times 1009$ (as prime factorization). Since $1009$ is an odd prime of the form $4k+1$, it can be written as a sum of two squares $1009 = a^2+b^2$. Together with $2 = 1^2 + 1^2$,
        Brahmagupta–Fibonacci identity
        $$(a^2+b^2)(c^2+d^2) = (ac-bd)^2 + (ad+bc)^2 = (ac+bd)^2 + (ad-bc)^2$$
        tell us $2018 = (a+b)^2 + (a-b)^2$.



        The task reduces to rewrite $1009$ as a sum of two squares. In addition to
        seaching by brute force, one can use algorithms described in
        answers of this question to determine $a,b$ efficiently. At the end, one find $$1009 = 28^2+15^2 quadimpliesquad 2018 = 43^2 + 13^2$$



        A good reference of these sort of algorithms will be Henri Cohen's book
        A course in Computation Algebraic Number Theory. Take a look at that if you need more details.







        share|cite|improve this answer














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        share|cite|improve this answer








        edited Nov 25 at 19:49









        LoPablo

        33




        33










        answered Dec 7 '17 at 4:51









        achille hui

        94.8k5129255




        94.8k5129255






























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