if $n = a_1a_2 cdots a_r + 2$, then $a_i nmid n$ for each integer $i (1 leq i leq r)$.












1












$begingroup$


Let $a_1, a_2, cdots , a_r$ be odd integers where $a_i > 1$ for $i = 1, 2, cdots , r$. Prove that if $n = a_1a_2 cdots a_r + 2$, then $a_i nmid n$ for each integer $i (1 leq i leq r)$.



Let $a_i mid n$, then $a_i mid a_1a_2 cdots a_r + 2$ also $a_i mid a_1a_2 cdots a_r$, thus $a_i mid a_1a_2 cdots a_r+2 - a_1a_2 cdots a_r implies a_i mid 2$, which is not possible since $a_i > 1$ is odd integer.



Is the logic correct?










share|cite|improve this question











$endgroup$












  • $begingroup$
    Yes. Alternatively by Euclid $,gcd(n,a_i) = gcd(2,a_i) $ by $ 2 = nbmod a_i $
    $endgroup$
    – Bill Dubuque
    Nov 28 '18 at 19:38


















1












$begingroup$


Let $a_1, a_2, cdots , a_r$ be odd integers where $a_i > 1$ for $i = 1, 2, cdots , r$. Prove that if $n = a_1a_2 cdots a_r + 2$, then $a_i nmid n$ for each integer $i (1 leq i leq r)$.



Let $a_i mid n$, then $a_i mid a_1a_2 cdots a_r + 2$ also $a_i mid a_1a_2 cdots a_r$, thus $a_i mid a_1a_2 cdots a_r+2 - a_1a_2 cdots a_r implies a_i mid 2$, which is not possible since $a_i > 1$ is odd integer.



Is the logic correct?










share|cite|improve this question











$endgroup$












  • $begingroup$
    Yes. Alternatively by Euclid $,gcd(n,a_i) = gcd(2,a_i) $ by $ 2 = nbmod a_i $
    $endgroup$
    – Bill Dubuque
    Nov 28 '18 at 19:38
















1












1








1





$begingroup$


Let $a_1, a_2, cdots , a_r$ be odd integers where $a_i > 1$ for $i = 1, 2, cdots , r$. Prove that if $n = a_1a_2 cdots a_r + 2$, then $a_i nmid n$ for each integer $i (1 leq i leq r)$.



Let $a_i mid n$, then $a_i mid a_1a_2 cdots a_r + 2$ also $a_i mid a_1a_2 cdots a_r$, thus $a_i mid a_1a_2 cdots a_r+2 - a_1a_2 cdots a_r implies a_i mid 2$, which is not possible since $a_i > 1$ is odd integer.



Is the logic correct?










share|cite|improve this question











$endgroup$




Let $a_1, a_2, cdots , a_r$ be odd integers where $a_i > 1$ for $i = 1, 2, cdots , r$. Prove that if $n = a_1a_2 cdots a_r + 2$, then $a_i nmid n$ for each integer $i (1 leq i leq r)$.



Let $a_i mid n$, then $a_i mid a_1a_2 cdots a_r + 2$ also $a_i mid a_1a_2 cdots a_r$, thus $a_i mid a_1a_2 cdots a_r+2 - a_1a_2 cdots a_r implies a_i mid 2$, which is not possible since $a_i > 1$ is odd integer.



Is the logic correct?







number-theory proof-verification divisibility integers






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Nov 28 '18 at 6:59









user26857

39.4k124183




39.4k124183










asked Nov 28 '18 at 6:11









user8795user8795

5,66462047




5,66462047












  • $begingroup$
    Yes. Alternatively by Euclid $,gcd(n,a_i) = gcd(2,a_i) $ by $ 2 = nbmod a_i $
    $endgroup$
    – Bill Dubuque
    Nov 28 '18 at 19:38




















  • $begingroup$
    Yes. Alternatively by Euclid $,gcd(n,a_i) = gcd(2,a_i) $ by $ 2 = nbmod a_i $
    $endgroup$
    – Bill Dubuque
    Nov 28 '18 at 19:38


















$begingroup$
Yes. Alternatively by Euclid $,gcd(n,a_i) = gcd(2,a_i) $ by $ 2 = nbmod a_i $
$endgroup$
– Bill Dubuque
Nov 28 '18 at 19:38






$begingroup$
Yes. Alternatively by Euclid $,gcd(n,a_i) = gcd(2,a_i) $ by $ 2 = nbmod a_i $
$endgroup$
– Bill Dubuque
Nov 28 '18 at 19:38












1 Answer
1






active

oldest

votes


















1












$begingroup$

Yes, your reasoning is sound and correct.






share|cite|improve this answer









$endgroup$













    Your Answer





    StackExchange.ifUsing("editor", function () {
    return StackExchange.using("mathjaxEditing", function () {
    StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
    StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
    });
    });
    }, "mathjax-editing");

    StackExchange.ready(function() {
    var channelOptions = {
    tags: "".split(" "),
    id: "69"
    };
    initTagRenderer("".split(" "), "".split(" "), channelOptions);

    StackExchange.using("externalEditor", function() {
    // Have to fire editor after snippets, if snippets enabled
    if (StackExchange.settings.snippets.snippetsEnabled) {
    StackExchange.using("snippets", function() {
    createEditor();
    });
    }
    else {
    createEditor();
    }
    });

    function createEditor() {
    StackExchange.prepareEditor({
    heartbeatType: 'answer',
    autoActivateHeartbeat: false,
    convertImagesToLinks: true,
    noModals: true,
    showLowRepImageUploadWarning: true,
    reputationToPostImages: 10,
    bindNavPrevention: true,
    postfix: "",
    imageUploader: {
    brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
    contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
    allowUrls: true
    },
    noCode: true, onDemand: true,
    discardSelector: ".discard-answer"
    ,immediatelyShowMarkdownHelp:true
    });


    }
    });














    draft saved

    draft discarded


















    StackExchange.ready(
    function () {
    StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3016797%2fif-n-a-1a-2-cdots-a-r-2-then-a-i-nmid-n-for-each-integer-i-1-leq-i%23new-answer', 'question_page');
    }
    );

    Post as a guest















    Required, but never shown

























    1 Answer
    1






    active

    oldest

    votes








    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    1












    $begingroup$

    Yes, your reasoning is sound and correct.






    share|cite|improve this answer









    $endgroup$


















      1












      $begingroup$

      Yes, your reasoning is sound and correct.






      share|cite|improve this answer









      $endgroup$
















        1












        1








        1





        $begingroup$

        Yes, your reasoning is sound and correct.






        share|cite|improve this answer









        $endgroup$



        Yes, your reasoning is sound and correct.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Nov 28 '18 at 6:12









        plattyplatty

        3,370320




        3,370320






























            draft saved

            draft discarded




















































            Thanks for contributing an answer to Mathematics Stack Exchange!


            • Please be sure to answer the question. Provide details and share your research!

            But avoid



            • Asking for help, clarification, or responding to other answers.

            • Making statements based on opinion; back them up with references or personal experience.


            Use MathJax to format equations. MathJax reference.


            To learn more, see our tips on writing great answers.




            draft saved


            draft discarded














            StackExchange.ready(
            function () {
            StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3016797%2fif-n-a-1a-2-cdots-a-r-2-then-a-i-nmid-n-for-each-integer-i-1-leq-i%23new-answer', 'question_page');
            }
            );

            Post as a guest















            Required, but never shown





















































            Required, but never shown














            Required, but never shown












            Required, but never shown







            Required, but never shown

































            Required, but never shown














            Required, but never shown












            Required, but never shown







            Required, but never shown







            Popular posts from this blog

            How to change which sound is reproduced for terminal bell?

            Can I use Tabulator js library in my java Spring + Thymeleaf project?

            Title Spacing in Bjornstrup Chapter, Removing Chapter Number From Contents