Non-linear differential equation with variable coefficient

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Given $$ xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$ What is the value of $x(2)$? I tried with $dx/dt=y, dy/dt=(dy/dx)(dx/dt)$ but failed at integration.







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    Given $$ xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$ What is the value of $x(2)$? I tried with $dx/dt=y, dy/dt=(dy/dx)(dx/dt)$ but failed at integration.







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      up vote
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      favorite
      1









      up vote
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      Given $$ xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$ What is the value of $x(2)$? I tried with $dx/dt=y, dy/dt=(dy/dx)(dx/dt)$ but failed at integration.







      share|cite|improve this question












      Given $$ xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$ What is the value of $x(2)$? I tried with $dx/dt=y, dy/dt=(dy/dx)(dx/dt)$ but failed at integration.









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      asked Aug 24 at 0:10









      Purushothaman

      1956




      1956




















          4 Answers
          4






          active

          oldest

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          up vote
          3
          down vote



          accepted










          Even if this is not a direct answer but it leads to the answer.



          This equation can be written as
          $$ dfracddt left( xdfracdxdt right)=xdfracdxdt,quad $$
          Therfore $ quad xdfracdxdt=ce^t $
          Then

          $$ int x dx = int ce^t dt$$
          so $$frac12x^2(t)=ce^t+d$$
          Can you take it from here?






          share|cite|improve this answer



























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            1
            down vote













            You can divide the equation by $xdotx$ and integrate the equation (chain rule).



            $$ fracddotxdotx + fracdotxx = 1 $$



            $$ implies ln(dotx) + ln(x) = ln(xdotx) = t+ c $$



            $$ implies xdotx = ke^t $$



            The last equation is separable again.






            share|cite|improve this answer



























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              Let$p=fracdxdt$ then $fracd^2xdt^2=p fracdpdx$ and the equation becomes
              begineqnarray*
              fracdpdx=fracx-px
              endeqnarray*
              or $p=0$. The equation above is easily solved by the substitution $p=xu$ ... good luck.






              share|cite|improve this answer



























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                $$xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$
                $$xx''+(x')^2=x'x$$
                $$implies (x'x)'=x'x$$
                Substitute $z=x'x$
                $$z'= z$$
                This last equation is separable...






                share|cite|improve this answer




















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                  4 Answers
                  4






                  active

                  oldest

                  votes








                  4 Answers
                  4






                  active

                  oldest

                  votes









                  active

                  oldest

                  votes






                  active

                  oldest

                  votes








                  up vote
                  3
                  down vote



                  accepted










                  Even if this is not a direct answer but it leads to the answer.



                  This equation can be written as
                  $$ dfracddt left( xdfracdxdt right)=xdfracdxdt,quad $$
                  Therfore $ quad xdfracdxdt=ce^t $
                  Then

                  $$ int x dx = int ce^t dt$$
                  so $$frac12x^2(t)=ce^t+d$$
                  Can you take it from here?






                  share|cite|improve this answer
























                    up vote
                    3
                    down vote



                    accepted










                    Even if this is not a direct answer but it leads to the answer.



                    This equation can be written as
                    $$ dfracddt left( xdfracdxdt right)=xdfracdxdt,quad $$
                    Therfore $ quad xdfracdxdt=ce^t $
                    Then

                    $$ int x dx = int ce^t dt$$
                    so $$frac12x^2(t)=ce^t+d$$
                    Can you take it from here?






                    share|cite|improve this answer






















                      up vote
                      3
                      down vote



                      accepted







                      up vote
                      3
                      down vote



                      accepted






                      Even if this is not a direct answer but it leads to the answer.



                      This equation can be written as
                      $$ dfracddt left( xdfracdxdt right)=xdfracdxdt,quad $$
                      Therfore $ quad xdfracdxdt=ce^t $
                      Then

                      $$ int x dx = int ce^t dt$$
                      so $$frac12x^2(t)=ce^t+d$$
                      Can you take it from here?






                      share|cite|improve this answer












                      Even if this is not a direct answer but it leads to the answer.



                      This equation can be written as
                      $$ dfracddt left( xdfracdxdt right)=xdfracdxdt,quad $$
                      Therfore $ quad xdfracdxdt=ce^t $
                      Then

                      $$ int x dx = int ce^t dt$$
                      so $$frac12x^2(t)=ce^t+d$$
                      Can you take it from here?







                      share|cite|improve this answer












                      share|cite|improve this answer



                      share|cite|improve this answer










                      answered Aug 24 at 0:33









                      The_lost

                      1,057318




                      1,057318




















                          up vote
                          1
                          down vote













                          You can divide the equation by $xdotx$ and integrate the equation (chain rule).



                          $$ fracddotxdotx + fracdotxx = 1 $$



                          $$ implies ln(dotx) + ln(x) = ln(xdotx) = t+ c $$



                          $$ implies xdotx = ke^t $$



                          The last equation is separable again.






                          share|cite|improve this answer
























                            up vote
                            1
                            down vote













                            You can divide the equation by $xdotx$ and integrate the equation (chain rule).



                            $$ fracddotxdotx + fracdotxx = 1 $$



                            $$ implies ln(dotx) + ln(x) = ln(xdotx) = t+ c $$



                            $$ implies xdotx = ke^t $$



                            The last equation is separable again.






                            share|cite|improve this answer






















                              up vote
                              1
                              down vote










                              up vote
                              1
                              down vote









                              You can divide the equation by $xdotx$ and integrate the equation (chain rule).



                              $$ fracddotxdotx + fracdotxx = 1 $$



                              $$ implies ln(dotx) + ln(x) = ln(xdotx) = t+ c $$



                              $$ implies xdotx = ke^t $$



                              The last equation is separable again.






                              share|cite|improve this answer












                              You can divide the equation by $xdotx$ and integrate the equation (chain rule).



                              $$ fracddotxdotx + fracdotxx = 1 $$



                              $$ implies ln(dotx) + ln(x) = ln(xdotx) = t+ c $$



                              $$ implies xdotx = ke^t $$



                              The last equation is separable again.







                              share|cite|improve this answer












                              share|cite|improve this answer



                              share|cite|improve this answer










                              answered Aug 24 at 1:05









                              zaphodxvii

                              1068




                              1068




















                                  up vote
                                  0
                                  down vote













                                  Let$p=fracdxdt$ then $fracd^2xdt^2=p fracdpdx$ and the equation becomes
                                  begineqnarray*
                                  fracdpdx=fracx-px
                                  endeqnarray*
                                  or $p=0$. The equation above is easily solved by the substitution $p=xu$ ... good luck.






                                  share|cite|improve this answer
























                                    up vote
                                    0
                                    down vote













                                    Let$p=fracdxdt$ then $fracd^2xdt^2=p fracdpdx$ and the equation becomes
                                    begineqnarray*
                                    fracdpdx=fracx-px
                                    endeqnarray*
                                    or $p=0$. The equation above is easily solved by the substitution $p=xu$ ... good luck.






                                    share|cite|improve this answer






















                                      up vote
                                      0
                                      down vote










                                      up vote
                                      0
                                      down vote









                                      Let$p=fracdxdt$ then $fracd^2xdt^2=p fracdpdx$ and the equation becomes
                                      begineqnarray*
                                      fracdpdx=fracx-px
                                      endeqnarray*
                                      or $p=0$. The equation above is easily solved by the substitution $p=xu$ ... good luck.






                                      share|cite|improve this answer












                                      Let$p=fracdxdt$ then $fracd^2xdt^2=p fracdpdx$ and the equation becomes
                                      begineqnarray*
                                      fracdpdx=fracx-px
                                      endeqnarray*
                                      or $p=0$. The equation above is easily solved by the substitution $p=xu$ ... good luck.







                                      share|cite|improve this answer












                                      share|cite|improve this answer



                                      share|cite|improve this answer










                                      answered Aug 24 at 0:21









                                      Donald Splutterwit

                                      21.4k21243




                                      21.4k21243




















                                          up vote
                                          0
                                          down vote













                                          $$xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$
                                          $$xx''+(x')^2=x'x$$
                                          $$implies (x'x)'=x'x$$
                                          Substitute $z=x'x$
                                          $$z'= z$$
                                          This last equation is separable...






                                          share|cite|improve this answer
























                                            up vote
                                            0
                                            down vote













                                            $$xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$
                                            $$xx''+(x')^2=x'x$$
                                            $$implies (x'x)'=x'x$$
                                            Substitute $z=x'x$
                                            $$z'= z$$
                                            This last equation is separable...






                                            share|cite|improve this answer






















                                              up vote
                                              0
                                              down vote










                                              up vote
                                              0
                                              down vote









                                              $$xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$
                                              $$xx''+(x')^2=x'x$$
                                              $$implies (x'x)'=x'x$$
                                              Substitute $z=x'x$
                                              $$z'= z$$
                                              This last equation is separable...






                                              share|cite|improve this answer












                                              $$xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$
                                              $$xx''+(x')^2=x'x$$
                                              $$implies (x'x)'=x'x$$
                                              Substitute $z=x'x$
                                              $$z'= z$$
                                              This last equation is separable...







                                              share|cite|improve this answer












                                              share|cite|improve this answer



                                              share|cite|improve this answer










                                              answered Aug 24 at 11:08









                                              Isham

                                              10.9k3929




                                              10.9k3929



























                                                   

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