# Is there enough information?

1. Jul 20, 2006

### natski

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

$$I=\int_{0}^{\infty}f(x)\ast g(x)\ast h(x)\ast dx$$

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

$$J=\int_{0}^{\infty}f(x)\ast g(x)\ast dx$$

and

$$K=\int_{0}^{\infty}f(x)\ast h(x)\ast dx$$

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

Natski

2. Jul 20, 2006

### natski

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

3. Jul 20, 2006

### StatusX

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.