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Help solving this differential equation

Hey there i'm looking for a solution to the following non-linear first order ODE.

(dydx)2=Aey+By+C (\frac{dy}{dx})^2 = Ae^{-y}+By+C

where A, B and C are constants.

Any ideas on how to solve this or if it's even got an analytical solution?
Original post by langlitz
Hey there i'm looking for a solution to the following non-linear first order ODE.

(dydx)2=Aey+By+C (\frac{dy}{dx})^2 = Ae^{-y}+By+C

where A, B and C are constants.

Any ideas on how to solve this or if it's even got an analytical solution?


As to whether this has an analytic form, I fed an example of an equation of this form to Mathematica, and it went away and thought for a while and returned with a simple re-write of the original equation. So, possibly not...
Original post by Gregorius
As to whether this has an analytic form, I fed an example of an equation of this form to Mathematica, and it went away and thought for a while and returned with a simple re-write of the original equation. So, possibly not...


It would be interesting to see whether other similar tools (eg. Maple/Matlab etc.), would have any more luck. (if anyone here has them)
Original post by langlitz
Hey there i'm looking for a solution to the following non-linear first order ODE.

(dydx)2=Aey+By+C (\frac{dy}{dx})^2 = Ae^{-y}+By+C

where A, B and C are constants.

Any ideas on how to solve this or if it's even got an analytical solution?


Isn't this equivalent to ±dyAey+By+C=x+D\pm \int \dfrac{dy}{\sqrt{Ae^{-y} + By +C}} = x+D? The integral doesn't look at all hopeful for a solution in terms of elementary functions.
Original post by atsruser
Isn't this equivalent to ±dyAey+By+C=x+D\pm \int \dfrac{dy}{\sqrt{Ae^{-y} + By +C}} = x+D? The integral doesn't look at all hopeful for a solution in terms of elementary functions.


Yup, that is what Mathematica returns...
Original post by Gregorius
Yup, that is what Mathematica returns...


Yeah, I was just trying to point out to the OP that it's fairly easy to see if it's likely to have a nice solution as it's separable.
Reply 6
Original post by atsruser
Isn't this equivalent to ±dyAey+By+C=x+D\pm \int \dfrac{dy}{\sqrt{Ae^{-y} + By +C}} = x+D? The integral doesn't look at all hopeful for a solution in terms of elementary functions.


Yep I was just wondering if there were any fancy methods for solving these kinds of equations which I don't know, wolfram alpha is not always foolproof for differential equations

I will try a numerical method :smile:
Original post by langlitz
I will try a numerical method :smile:

I suspect that's the only real possibility here, if you need a solution.

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