# Need help with inverse laplace transformation

1. Nov 27, 2008

### Karmel

1. The problem statement, all variables and given/known data
(s^3+6s^2-18s+13)/(s(s+1)(s^2-4s+13)

2. Relevant equations

3. The attempt at a solution
I am so lost on this problem. I have tried it several times and just keep confusing myself. I think that I am messing up jsut setting up the problem. Can someone please help me out? How do I get this into partial fraction and then where do I go from there.

2. Nov 28, 2008

### Unco

Hi Karmel,

Assuming you want to take the inverse Laplace transform of F(s) = (s^3+6s^2-18s+13)/(s(s+1)(s^2-4s+13)), the first step is to decompose it into partial fractions, which I'm sure you would have come across before. There are three such partial fractions, of the form A/s, B/(s+1) and (Cs+D)/(s^2-4s+13), with A, B, C and D constants to be determined.

Show us your work so we know where you're getting stuck.

3. Nov 30, 2008

### Karmel

I would love to show my work but after I set it up like showed to me above with the partial fraction I dont know what to do. The book I am using is so unclear on partial fractions. What are the steps?

4. Dec 1, 2008

### Karmel

so after doing the partial fractions if I am doing it right I get teh final answer to be

1-e^-s+(s+4)(sin(3s)(e2s)/3)

I really hope that is right cause I have tried it a thousand ways and Iam getting no where....

5. Dec 2, 2008

### Defennder

You can check your answer using this online calculator:

I don't know if that link would expire over time, but if it does, just head to the main page and look for the online Fourier-Laplace calculator. Apart from that I'm kind of lazy to work it out.

6. Jan 8, 2010

### friend sultan

(s^2+2s+1)/(s^3+2s^2+4s+2)

7. Jan 9, 2010

### friend sultan

(s^2+2s+1)/(s^3)+2(s^2)+4s+2)

8. Jan 9, 2010

### friend sultan

(s^2+2s+1)/((s^3)+2(s^2)+4s+2)

9. Dec 12, 2010

### zeroone_1343

can anyone help with this
s((s-a)^0.5)