@mmcdara 

It is enough to calculate deq minus eq and the integral is gone. The task doesn't require any more tricks.

@mehdi jafari 

... us have a look ;-)

@Kitonum 

Yes, there is power in these Maple commands. In the past, the formation law had to be laboriously determined using the characteristic equation (literature e.g. Markuschewitsch, Lin. Rekursionen). It is important that pupils and students learn this background-knowledge in order to be able to use it if the computer breaks down ;-).

@salim-barzani 

...wavelets? I have no experience with solitons in solving methods. But as far as I can remember, there are methods that use wavelets, e.g.:

https://ijsts.shirazu.ac.ir/article_2153_836c1c7bda66ef58fcead78d7a6f9f97.pdf

Maple offers something about this in the help.
Good luck!

@salim-barzani 

..., but I can't help you with that. I was only interested in solving your equation out of curiosity in memory of "old times" even without knowing your specific physics background.
Finally, a link:
https://www.colorado.edu/amath/sites/default/files/attached-files/2015_uc-london.pdf

@salim-barzani 

I wrote Painleve Type II! A square of the first derivative is not included in this equation structure.

You want to calculate the zeros of a 4th degree polynomial. This is possible in principle, but results in terribly long formulas (https://en.wikipedia.org/wiki/Quartic_equation). It would be much easier to treat each specific case numerically.

The vibration behavior of thin elastic plates is probably to be investigated. To do this, the geometry/contour and the bearing/support as well as material properties must be specified. The plate behavior is then described by a well-known so-called plate equation (partial differential equation). Do natural frequencies have to be determined or is there an excitation load? Is damping present? There is extensive literature on this. I recommend "Werner, Structural Dynamics" page 146 and "Szabo, Advanced Technical Mechanics".

You should write this down on a worksheet to start with. Then we will move on and solve the equation.

The conditions of the Picard-Lindelöf theorem are crucial for the existence and uniqueness of an explicit solution to the given differential equation. In the present case, under the current initial conditions, these are only fulfilled in a rectangle of the x-y coordinate system with approximately 0<=x<62 and -18<y<57. Only in this field does a consistent direction field exist. As a Maple newbie, I don't know how to plot an implicit function, so I did this with the help of good old derive. If you leave out this rectangle restriction, the graph is obviously ambiguous. Maple probably has problems with this and therefore does not allow a solution for y(x).

@janhardo 

Yes, but that doesn't make the solution any easier. Only the numerical approach will probably lead to the goal.

Here are my solutions:

@mmcdara 

The solution deserves several thumbs up. Where can I type that in?

@Rouben Rostamian  

That is great :-)

@vv 

One solution would be to calculate it in detail ;-) . Question: How long is a coastline that is being measured in ever greater detail? What happens with polygon in lim ---> oo ?

@Carl Love 

No rings - or topologically equivalent figures of higher genus, otherwise everything is allowed.