Solve the non-linear DE $y' = xy+ y^{1/2}$ analytically [closed]












0














I've tried the Bernoulli Eq technique, $y=ux$ substitution technique, but nothing seemed to work out. Any ideas?










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closed as off-topic by José Carlos Santos, Henrik, Vidyanshu Mishra, Saad, amWhy Nov 30 at 15:04


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is missing context or other details: Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience level." – José Carlos Santos, Henrik, Vidyanshu Mishra, Saad, amWhy

If this question can be reworded to fit the rules in the help center, please edit the question.













  • I take it that you think of $y'=xy+y^{1/2}$ otherwise the equation is linear.
    – Martin
    Nov 30 at 6:07










  • @Kenisha please check if the formatting corresponds to your DE.
    – user376343
    Nov 30 at 6:14
















0














I've tried the Bernoulli Eq technique, $y=ux$ substitution technique, but nothing seemed to work out. Any ideas?










share|cite|improve this question















closed as off-topic by José Carlos Santos, Henrik, Vidyanshu Mishra, Saad, amWhy Nov 30 at 15:04


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is missing context or other details: Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience level." – José Carlos Santos, Henrik, Vidyanshu Mishra, Saad, amWhy

If this question can be reworded to fit the rules in the help center, please edit the question.













  • I take it that you think of $y'=xy+y^{1/2}$ otherwise the equation is linear.
    – Martin
    Nov 30 at 6:07










  • @Kenisha please check if the formatting corresponds to your DE.
    – user376343
    Nov 30 at 6:14














0












0








0







I've tried the Bernoulli Eq technique, $y=ux$ substitution technique, but nothing seemed to work out. Any ideas?










share|cite|improve this question















I've tried the Bernoulli Eq technique, $y=ux$ substitution technique, but nothing seemed to work out. Any ideas?







differential-equations






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edited Nov 30 at 6:12









user376343

2,7782822




2,7782822










asked Nov 30 at 5:59









Kenisha Stills

111




111




closed as off-topic by José Carlos Santos, Henrik, Vidyanshu Mishra, Saad, amWhy Nov 30 at 15:04


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is missing context or other details: Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience level." – José Carlos Santos, Henrik, Vidyanshu Mishra, Saad, amWhy

If this question can be reworded to fit the rules in the help center, please edit the question.




closed as off-topic by José Carlos Santos, Henrik, Vidyanshu Mishra, Saad, amWhy Nov 30 at 15:04


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is missing context or other details: Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience level." – José Carlos Santos, Henrik, Vidyanshu Mishra, Saad, amWhy

If this question can be reworded to fit the rules in the help center, please edit the question.












  • I take it that you think of $y'=xy+y^{1/2}$ otherwise the equation is linear.
    – Martin
    Nov 30 at 6:07










  • @Kenisha please check if the formatting corresponds to your DE.
    – user376343
    Nov 30 at 6:14


















  • I take it that you think of $y'=xy+y^{1/2}$ otherwise the equation is linear.
    – Martin
    Nov 30 at 6:07










  • @Kenisha please check if the formatting corresponds to your DE.
    – user376343
    Nov 30 at 6:14
















I take it that you think of $y'=xy+y^{1/2}$ otherwise the equation is linear.
– Martin
Nov 30 at 6:07




I take it that you think of $y'=xy+y^{1/2}$ otherwise the equation is linear.
– Martin
Nov 30 at 6:07












@Kenisha please check if the formatting corresponds to your DE.
– user376343
Nov 30 at 6:14




@Kenisha please check if the formatting corresponds to your DE.
– user376343
Nov 30 at 6:14










3 Answers
3






active

oldest

votes


















2














Put $y=u^2$ so $y'=2uu'=xu^2+uRightarrow u'=frac 12xu+frac12$. Solve for $u$ using integrating factor and then find $y$.






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    0














    $y'=xy+y^{1/2} implies y'-xy=y^{1/2}$



    So taking $p(x)=-x,q(x)=1, n={1/2}$



    We have $y'+p(x)=q(x)y^n$



    Applying Bernoulli's Equation



    $$y^{1-n}=frac{(1-n)int e^{(1-n)int p(x)dx}q(x)dx+c_1}{e^{(1-n)int p(x)dx}}$$



    Plugging in some terms we get
    $$y^{1/2}=frac{(1/2)int e^{(-x^2/4)}dx+c_1}{e^{(-x^2/4)}}$$



    $$y^{1/2}=frac{(sqrt{pi}/2)operatorname{erf}(x/2)+c_1}{e^{(-x^2/4)}}$$



    $$y^{1/2}=e^{(x^2/4)}bigg((sqrt{pi}/2)operatorname{erf}(x/2)+c_1 bigg)$$



    $$y=frac{pi}{4}e^{(x^2/2)}bigg(operatorname{erf}(x/2)+c_1 bigg)^2$$



    Where $operatorname{erf}(z) =frac{2}{sqrt{pi}} int_0^z e^{-t^2} dt $ is the error function






    share|cite|improve this answer





























      0














      As Guacho Perez answered, starting with $y=u^2$, you end with



      $$u left(-2 u'+x u+1right)=0$$ Excluding the trivial case $u=0$, you then need to solve
      $$2u'-xu=-1$$ Consider first
      $$2u'-xu=0 implies frac{u'}u=frac x 2implies log(u)=frac {x^2} 4+Cimplies u=C e^{frac{x^2}{4}}$$ Now, use the integration factor or the variation of parameters to get
      $$2 e^{frac{x^2}{4}} C'(x)=1implies C'=frac 12 e^{-frac{x^2}{4}}implies C=frac{sqrt{pi }}{2} text{erf}left(frac{x}{2}right)+K$$ then $u$ and $y$






      share|cite|improve this answer





















      • I'm probably not at as great as a school as you've all attended. I'm in Ohio. I haven't been taught error functions nor was aware of them.
        – Kenisha Stills
        Nov 30 at 12:36


















      3 Answers
      3






      active

      oldest

      votes








      3 Answers
      3






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes









      2














      Put $y=u^2$ so $y'=2uu'=xu^2+uRightarrow u'=frac 12xu+frac12$. Solve for $u$ using integrating factor and then find $y$.






      share|cite|improve this answer


























        2














        Put $y=u^2$ so $y'=2uu'=xu^2+uRightarrow u'=frac 12xu+frac12$. Solve for $u$ using integrating factor and then find $y$.






        share|cite|improve this answer
























          2












          2








          2






          Put $y=u^2$ so $y'=2uu'=xu^2+uRightarrow u'=frac 12xu+frac12$. Solve for $u$ using integrating factor and then find $y$.






          share|cite|improve this answer












          Put $y=u^2$ so $y'=2uu'=xu^2+uRightarrow u'=frac 12xu+frac12$. Solve for $u$ using integrating factor and then find $y$.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Nov 30 at 6:27









          Guacho Perez

          3,88911131




          3,88911131























              0














              $y'=xy+y^{1/2} implies y'-xy=y^{1/2}$



              So taking $p(x)=-x,q(x)=1, n={1/2}$



              We have $y'+p(x)=q(x)y^n$



              Applying Bernoulli's Equation



              $$y^{1-n}=frac{(1-n)int e^{(1-n)int p(x)dx}q(x)dx+c_1}{e^{(1-n)int p(x)dx}}$$



              Plugging in some terms we get
              $$y^{1/2}=frac{(1/2)int e^{(-x^2/4)}dx+c_1}{e^{(-x^2/4)}}$$



              $$y^{1/2}=frac{(sqrt{pi}/2)operatorname{erf}(x/2)+c_1}{e^{(-x^2/4)}}$$



              $$y^{1/2}=e^{(x^2/4)}bigg((sqrt{pi}/2)operatorname{erf}(x/2)+c_1 bigg)$$



              $$y=frac{pi}{4}e^{(x^2/2)}bigg(operatorname{erf}(x/2)+c_1 bigg)^2$$



              Where $operatorname{erf}(z) =frac{2}{sqrt{pi}} int_0^z e^{-t^2} dt $ is the error function






              share|cite|improve this answer


























                0














                $y'=xy+y^{1/2} implies y'-xy=y^{1/2}$



                So taking $p(x)=-x,q(x)=1, n={1/2}$



                We have $y'+p(x)=q(x)y^n$



                Applying Bernoulli's Equation



                $$y^{1-n}=frac{(1-n)int e^{(1-n)int p(x)dx}q(x)dx+c_1}{e^{(1-n)int p(x)dx}}$$



                Plugging in some terms we get
                $$y^{1/2}=frac{(1/2)int e^{(-x^2/4)}dx+c_1}{e^{(-x^2/4)}}$$



                $$y^{1/2}=frac{(sqrt{pi}/2)operatorname{erf}(x/2)+c_1}{e^{(-x^2/4)}}$$



                $$y^{1/2}=e^{(x^2/4)}bigg((sqrt{pi}/2)operatorname{erf}(x/2)+c_1 bigg)$$



                $$y=frac{pi}{4}e^{(x^2/2)}bigg(operatorname{erf}(x/2)+c_1 bigg)^2$$



                Where $operatorname{erf}(z) =frac{2}{sqrt{pi}} int_0^z e^{-t^2} dt $ is the error function






                share|cite|improve this answer
























                  0












                  0








                  0






                  $y'=xy+y^{1/2} implies y'-xy=y^{1/2}$



                  So taking $p(x)=-x,q(x)=1, n={1/2}$



                  We have $y'+p(x)=q(x)y^n$



                  Applying Bernoulli's Equation



                  $$y^{1-n}=frac{(1-n)int e^{(1-n)int p(x)dx}q(x)dx+c_1}{e^{(1-n)int p(x)dx}}$$



                  Plugging in some terms we get
                  $$y^{1/2}=frac{(1/2)int e^{(-x^2/4)}dx+c_1}{e^{(-x^2/4)}}$$



                  $$y^{1/2}=frac{(sqrt{pi}/2)operatorname{erf}(x/2)+c_1}{e^{(-x^2/4)}}$$



                  $$y^{1/2}=e^{(x^2/4)}bigg((sqrt{pi}/2)operatorname{erf}(x/2)+c_1 bigg)$$



                  $$y=frac{pi}{4}e^{(x^2/2)}bigg(operatorname{erf}(x/2)+c_1 bigg)^2$$



                  Where $operatorname{erf}(z) =frac{2}{sqrt{pi}} int_0^z e^{-t^2} dt $ is the error function






                  share|cite|improve this answer












                  $y'=xy+y^{1/2} implies y'-xy=y^{1/2}$



                  So taking $p(x)=-x,q(x)=1, n={1/2}$



                  We have $y'+p(x)=q(x)y^n$



                  Applying Bernoulli's Equation



                  $$y^{1-n}=frac{(1-n)int e^{(1-n)int p(x)dx}q(x)dx+c_1}{e^{(1-n)int p(x)dx}}$$



                  Plugging in some terms we get
                  $$y^{1/2}=frac{(1/2)int e^{(-x^2/4)}dx+c_1}{e^{(-x^2/4)}}$$



                  $$y^{1/2}=frac{(sqrt{pi}/2)operatorname{erf}(x/2)+c_1}{e^{(-x^2/4)}}$$



                  $$y^{1/2}=e^{(x^2/4)}bigg((sqrt{pi}/2)operatorname{erf}(x/2)+c_1 bigg)$$



                  $$y=frac{pi}{4}e^{(x^2/2)}bigg(operatorname{erf}(x/2)+c_1 bigg)^2$$



                  Where $operatorname{erf}(z) =frac{2}{sqrt{pi}} int_0^z e^{-t^2} dt $ is the error function







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered Nov 30 at 6:41









                  Mason

                  1,9341530




                  1,9341530























                      0














                      As Guacho Perez answered, starting with $y=u^2$, you end with



                      $$u left(-2 u'+x u+1right)=0$$ Excluding the trivial case $u=0$, you then need to solve
                      $$2u'-xu=-1$$ Consider first
                      $$2u'-xu=0 implies frac{u'}u=frac x 2implies log(u)=frac {x^2} 4+Cimplies u=C e^{frac{x^2}{4}}$$ Now, use the integration factor or the variation of parameters to get
                      $$2 e^{frac{x^2}{4}} C'(x)=1implies C'=frac 12 e^{-frac{x^2}{4}}implies C=frac{sqrt{pi }}{2} text{erf}left(frac{x}{2}right)+K$$ then $u$ and $y$






                      share|cite|improve this answer





















                      • I'm probably not at as great as a school as you've all attended. I'm in Ohio. I haven't been taught error functions nor was aware of them.
                        – Kenisha Stills
                        Nov 30 at 12:36
















                      0














                      As Guacho Perez answered, starting with $y=u^2$, you end with



                      $$u left(-2 u'+x u+1right)=0$$ Excluding the trivial case $u=0$, you then need to solve
                      $$2u'-xu=-1$$ Consider first
                      $$2u'-xu=0 implies frac{u'}u=frac x 2implies log(u)=frac {x^2} 4+Cimplies u=C e^{frac{x^2}{4}}$$ Now, use the integration factor or the variation of parameters to get
                      $$2 e^{frac{x^2}{4}} C'(x)=1implies C'=frac 12 e^{-frac{x^2}{4}}implies C=frac{sqrt{pi }}{2} text{erf}left(frac{x}{2}right)+K$$ then $u$ and $y$






                      share|cite|improve this answer





















                      • I'm probably not at as great as a school as you've all attended. I'm in Ohio. I haven't been taught error functions nor was aware of them.
                        – Kenisha Stills
                        Nov 30 at 12:36














                      0












                      0








                      0






                      As Guacho Perez answered, starting with $y=u^2$, you end with



                      $$u left(-2 u'+x u+1right)=0$$ Excluding the trivial case $u=0$, you then need to solve
                      $$2u'-xu=-1$$ Consider first
                      $$2u'-xu=0 implies frac{u'}u=frac x 2implies log(u)=frac {x^2} 4+Cimplies u=C e^{frac{x^2}{4}}$$ Now, use the integration factor or the variation of parameters to get
                      $$2 e^{frac{x^2}{4}} C'(x)=1implies C'=frac 12 e^{-frac{x^2}{4}}implies C=frac{sqrt{pi }}{2} text{erf}left(frac{x}{2}right)+K$$ then $u$ and $y$






                      share|cite|improve this answer












                      As Guacho Perez answered, starting with $y=u^2$, you end with



                      $$u left(-2 u'+x u+1right)=0$$ Excluding the trivial case $u=0$, you then need to solve
                      $$2u'-xu=-1$$ Consider first
                      $$2u'-xu=0 implies frac{u'}u=frac x 2implies log(u)=frac {x^2} 4+Cimplies u=C e^{frac{x^2}{4}}$$ Now, use the integration factor or the variation of parameters to get
                      $$2 e^{frac{x^2}{4}} C'(x)=1implies C'=frac 12 e^{-frac{x^2}{4}}implies C=frac{sqrt{pi }}{2} text{erf}left(frac{x}{2}right)+K$$ then $u$ and $y$







                      share|cite|improve this answer












                      share|cite|improve this answer



                      share|cite|improve this answer










                      answered Nov 30 at 6:50









                      Claude Leibovici

                      119k1157132




                      119k1157132












                      • I'm probably not at as great as a school as you've all attended. I'm in Ohio. I haven't been taught error functions nor was aware of them.
                        – Kenisha Stills
                        Nov 30 at 12:36


















                      • I'm probably not at as great as a school as you've all attended. I'm in Ohio. I haven't been taught error functions nor was aware of them.
                        – Kenisha Stills
                        Nov 30 at 12:36
















                      I'm probably not at as great as a school as you've all attended. I'm in Ohio. I haven't been taught error functions nor was aware of them.
                      – Kenisha Stills
                      Nov 30 at 12:36




                      I'm probably not at as great as a school as you've all attended. I'm in Ohio. I haven't been taught error functions nor was aware of them.
                      – Kenisha Stills
                      Nov 30 at 12:36



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