Can I be Expressed in Terms of J and K for Arbitrary f,g,h?

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The discussion centers on the mathematical integration of three functions, specifically whether the integral I, defined as I=\int_{0}^{\infty}f(x)\ast g(x)\ast h(x)\ast dx, can be expressed in terms of J and K, where J=\int_{0}^{\infty}f(x)\ast g(x)\ast dx and K=\int_{0}^{\infty}f(x)\ast h(x)\ast dx. Natski concludes that it is not possible to express I in terms of J and K for arbitrary functions f, g, and h, providing a counterexample by setting f=1 and demonstrating the limitations of integration by parts.

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natski
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Hi, I have been thinking recently about integrating something with 3 parts such as:

[tex]I=\int_{0}^{\infty}f(x)\ast g(x)\ast h(x)\ast dx[/tex]

If I is an unknown that we are trying to find and we know what J and K are where:

[tex]J=\int_{0}^{\infty}f(x)\ast g(x)\ast dx[/tex]

and

[tex]K=\int_{0}^{\infty}f(x)\ast h(x)\ast dx[/tex]

Is there enough information to find I? (Note how we cannot get rid of or change the limits).

Natski
 
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assume...

Just to add, we assume that each function is easy to differentiate or integrate by itself but the three functions multiplies is too difficult.

Natski
 
If your question is, can you express I in terms of J and K for arbitrary f,g,h, the answer is no. One easy was to see this is by letting f=1. You can still integrate by parts if you use something like u=f(x)g(x), du=h(x)dx.
 

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