I have problems solving:

Seperating variables gives:

But unfortunately, ...I'm not sure if we're able to integrate w.r.t

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- Nov 3rd 2010, 11:17 AMDinkydoeComplex variable...
I have problems solving:

Seperating variables gives:

But unfortunately, ...I'm not sure if we're able to integrate w.r.t - Nov 3rd 2010, 11:58 AMAckbeet
Just a shot in the dark here, but what about this:

- Nov 3rd 2010, 12:18 PMDinkydoe
Thanks for the suggestion...but then again: Integrating w.r.t z is also a problem I wouldn't know how to solve..

The actual thing I'm trying to show here, is that not all solutions to this equation are bounded..., the question asks to solve the eq. explicitly

But I've no clue how. However, we may be able to use that for all t..., then try to show that all solution except the origin are unbounded.

(edit: i meant to show that not all solutions to this problem are bounded) - Nov 3rd 2010, 11:45 PMProve It
is a constant.

So you should get

- Nov 4th 2010, 02:25 AMDinkydoe
I don't fully understand. I agree if you said:

I don't see why you could just treat as a constant. It's a real number depending on z. So why is it you can treat it as such?

...is this really true? - Nov 4th 2010, 03:36 AMAckbeet
I'm with dinkydoe on this one. I would agree, from the DE, that

is a constant. But I don't see how you can get that is a constant. - Nov 4th 2010, 06:21 AMDinkydoe
Ok, so my professor hinted to something like a substitution . Then

So we have

So...

And finally ..

But i'm not even sure if this is a valid way of arguing...Furthermore, doesn't this generate only bounded solutions. - Nov 4th 2010, 07:00 AMAckbeet
Yeah, I was thinking of a substitution somewhat like that, but I ran into difficulties. That one is better, I think. Query: does your solution satisfy the original DE?

I'm not so sure that this generates only bounded solutions. You don't know that the exponent there is purely imaginary, do you?