understanding the proof using the mean value theorem in the economic paper.












1












$begingroup$



enter image description here




This is the economic paper: Hopkins and Kornienko (2004): Running to Keep in the same place. The picture shows the proof of the proposition 1 in this paper. In this proof, I don't understand how the mean value theorem is applied.



Here is my attempt to understand the proof and I am considering the first inequality:
By mean value theorem,
$$V(x(z), z-px(z))(alpha + G(z)) - V(x(check{z}), z - px(check{z}))(alpha + G(check{z})) - [(x(z) - x(hat{z})][V_1(x(tilde{z}), z - px(tilde{z})) - pV_2(x(tilde{z}), z - px(tilde{z}))](alpha + G(z))=0, $$



where $tilde{z} in (z, hat{z})$. Then, I think they try to make this bigger or equal than 0:



$$ V(x(z), z-px(z))(alpha + G(z)) - V(x(check{z}), z - px(check{z}))(alpha + G(check{z})) le V(x(z), z-px(z))[G(z) - G(hat{z})], $$



and



$$-[(x(z) - x(hat{z})][V_1(x(tilde{z}), z - px(tilde{z})) - pV_2(x(tilde{z}), z - px(tilde{z}))](alpha + G(z)) le -[(x(z) - x(hat{z})][V_1(x(tilde{z}), z - px(tilde{z})) - pV_2(x(tilde{z}), z - px(tilde{z}))](alpha + G(hat{z})).$$



But, both are wrong because by assumption, $ V(x(z), z-px(z)) ge V(x(check{z}), z - px(check{z}))$, and $G(z)$ is strictly increasing.



If this is wrong, I don't understand what's going on here. Am I missing something in MVT?



I appreciate if you give any help.










share|cite|improve this question









$endgroup$

















    1












    $begingroup$



    enter image description here




    This is the economic paper: Hopkins and Kornienko (2004): Running to Keep in the same place. The picture shows the proof of the proposition 1 in this paper. In this proof, I don't understand how the mean value theorem is applied.



    Here is my attempt to understand the proof and I am considering the first inequality:
    By mean value theorem,
    $$V(x(z), z-px(z))(alpha + G(z)) - V(x(check{z}), z - px(check{z}))(alpha + G(check{z})) - [(x(z) - x(hat{z})][V_1(x(tilde{z}), z - px(tilde{z})) - pV_2(x(tilde{z}), z - px(tilde{z}))](alpha + G(z))=0, $$



    where $tilde{z} in (z, hat{z})$. Then, I think they try to make this bigger or equal than 0:



    $$ V(x(z), z-px(z))(alpha + G(z)) - V(x(check{z}), z - px(check{z}))(alpha + G(check{z})) le V(x(z), z-px(z))[G(z) - G(hat{z})], $$



    and



    $$-[(x(z) - x(hat{z})][V_1(x(tilde{z}), z - px(tilde{z})) - pV_2(x(tilde{z}), z - px(tilde{z}))](alpha + G(z)) le -[(x(z) - x(hat{z})][V_1(x(tilde{z}), z - px(tilde{z})) - pV_2(x(tilde{z}), z - px(tilde{z}))](alpha + G(hat{z})).$$



    But, both are wrong because by assumption, $ V(x(z), z-px(z)) ge V(x(check{z}), z - px(check{z}))$, and $G(z)$ is strictly increasing.



    If this is wrong, I don't understand what's going on here. Am I missing something in MVT?



    I appreciate if you give any help.










    share|cite|improve this question









    $endgroup$















      1












      1








      1





      $begingroup$



      enter image description here




      This is the economic paper: Hopkins and Kornienko (2004): Running to Keep in the same place. The picture shows the proof of the proposition 1 in this paper. In this proof, I don't understand how the mean value theorem is applied.



      Here is my attempt to understand the proof and I am considering the first inequality:
      By mean value theorem,
      $$V(x(z), z-px(z))(alpha + G(z)) - V(x(check{z}), z - px(check{z}))(alpha + G(check{z})) - [(x(z) - x(hat{z})][V_1(x(tilde{z}), z - px(tilde{z})) - pV_2(x(tilde{z}), z - px(tilde{z}))](alpha + G(z))=0, $$



      where $tilde{z} in (z, hat{z})$. Then, I think they try to make this bigger or equal than 0:



      $$ V(x(z), z-px(z))(alpha + G(z)) - V(x(check{z}), z - px(check{z}))(alpha + G(check{z})) le V(x(z), z-px(z))[G(z) - G(hat{z})], $$



      and



      $$-[(x(z) - x(hat{z})][V_1(x(tilde{z}), z - px(tilde{z})) - pV_2(x(tilde{z}), z - px(tilde{z}))](alpha + G(z)) le -[(x(z) - x(hat{z})][V_1(x(tilde{z}), z - px(tilde{z})) - pV_2(x(tilde{z}), z - px(tilde{z}))](alpha + G(hat{z})).$$



      But, both are wrong because by assumption, $ V(x(z), z-px(z)) ge V(x(check{z}), z - px(check{z}))$, and $G(z)$ is strictly increasing.



      If this is wrong, I don't understand what's going on here. Am I missing something in MVT?



      I appreciate if you give any help.










      share|cite|improve this question









      $endgroup$





      enter image description here




      This is the economic paper: Hopkins and Kornienko (2004): Running to Keep in the same place. The picture shows the proof of the proposition 1 in this paper. In this proof, I don't understand how the mean value theorem is applied.



      Here is my attempt to understand the proof and I am considering the first inequality:
      By mean value theorem,
      $$V(x(z), z-px(z))(alpha + G(z)) - V(x(check{z}), z - px(check{z}))(alpha + G(check{z})) - [(x(z) - x(hat{z})][V_1(x(tilde{z}), z - px(tilde{z})) - pV_2(x(tilde{z}), z - px(tilde{z}))](alpha + G(z))=0, $$



      where $tilde{z} in (z, hat{z})$. Then, I think they try to make this bigger or equal than 0:



      $$ V(x(z), z-px(z))(alpha + G(z)) - V(x(check{z}), z - px(check{z}))(alpha + G(check{z})) le V(x(z), z-px(z))[G(z) - G(hat{z})], $$



      and



      $$-[(x(z) - x(hat{z})][V_1(x(tilde{z}), z - px(tilde{z})) - pV_2(x(tilde{z}), z - px(tilde{z}))](alpha + G(z)) le -[(x(z) - x(hat{z})][V_1(x(tilde{z}), z - px(tilde{z})) - pV_2(x(tilde{z}), z - px(tilde{z}))](alpha + G(hat{z})).$$



      But, both are wrong because by assumption, $ V(x(z), z-px(z)) ge V(x(check{z}), z - px(check{z}))$, and $G(z)$ is strictly increasing.



      If this is wrong, I don't understand what's going on here. Am I missing something in MVT?



      I appreciate if you give any help.







      real-analysis derivatives economics






      share|cite|improve this question













      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Jan 31 at 6:02









      DaeseonDaeseon

      855311




      855311






















          0






          active

          oldest

          votes












          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%2f3094568%2funderstanding-the-proof-using-the-mean-value-theorem-in-the-economic-paper%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown

























          0






          active

          oldest

          votes








          0






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes
















          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%2f3094568%2funderstanding-the-proof-using-the-mean-value-theorem-in-the-economic-paper%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

          MongoDB - Not Authorized To Execute Command

          How to fix TextFormField cause rebuild widget in Flutter

          Npm cannot find a required file even through it is in the searched directory