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Homework Statement
Show that if [itex] \lambda > \frac{1}{2} [/itex] there does not exist a real-valued function 'u' such that for all x in the closed interval [itex] 0 <= x <= 1 [/itex], [itex] u(x) = 1 + \lambda\int_{x}^{1} u(y)u(y-x)\,dy [/itex]
Homework Equations
The Attempt at a Solution
I started off by assuming that such a function does in fact exist, so:
[itex] u(x) = 1 + \lambda\int_{x}^{1}u(y)u(y-x)\,dy [/itex]
[itex] \lambda > \frac{1}{2} [/itex]
[itex] 0 <= x <= 1[/itex]
[itex] \mu = \int_{0}^{1} u(x)\,dx [/itex]
[itex] = \int_{0}^{1}\,dx + \int_{0}^{1}\int_{x}^{1} u(y)u(y-x) dy \hspace{1 mm} dx [/itex]
Here, I changed the order of integration:
[itex] = 1 + \lambda\int_{0}^{1}\int_{0}^{y} u(y)u(y-x)dx \hspace{1 mm} dy [/itex]
[itex] = 1 + \lambda\int_{0}^{1}u(y)\int_{0}^{y}u(y-x)dx \hspace{1 mm} dy [/itex]
At this point I am a bit confused about where to go, so I am starting to think that perhaps I am not going in the right direction; I was hoping someone could give me some advice. Thanks :)