# Thread: Convolution

1. ## Convolution

Hey.
How can I solve this problem using Convolution?

2. Originally Posted by asi123
Hey.
How can I solve this problem using Convolution?
Do you have to use convolution? Why not break it up into partial fractions ....?

$\displaystyle \frac{5s}{(s^2 + 9) (s - 4)} = \frac{as+b}{s^2 + 9} + \frac{c}{s-4} = a \, \frac{s}{s^2 + 3^2} + \frac{b}{3} \, \frac{3}{s^2 + 3^2} + \frac{c}{s + (-4)}$ ....

If you must use convolutions, I'd note that $\displaystyle \frac{5s}{(s^2 + 9) (s - 4)} = 5 \, \frac{s}{s^2 + 3^2} \cdot \frac{1}{s + (-4)}$ and apply the convolution theorem ......

3. Originally Posted by asi123
Hey.
How can I solve this problem using Convolution?
Mr Fantastic appears to know what you are talking about, but I do not see a problem just a Laplace transform or transfer function. So what are we being asked to solve using convolution?

If you want to find the function that this is the LT of using the convolution theorem you need to know that this is it or equation 10 here.

RonL

4. Originally Posted by CaptainBlack
Mr Fantastic appears to know what you are talking about, but I do not see a problem just a Laplace transform or transfer function. So what are we being asked to solve using convolution?

If you want to find the function that this is the LT of using the convolution theorem you need to know that this is it or equation 10 here.

RonL
As is often the case, appearances can be deceiving lol!

Actually I was going to ask for more information, then decided it was probably an inverse Laplace transform problem and posted accordingly. I guess we'll find out soon enough ......