# Finding partial fraction expansions

1. Feb 4, 2009

### smalllittle

1. The problem statement, all variables and given/known data

3. Find the partial fraction expansions of the following polynomials

a) 10/[(s^2)(s^2+6s+10)]

3. The attempt at a solution
I assume i should expan the polynomial in the form A/s^2+B/s+(Cs+D)/(s^2+6s+10) but i stuck at finding B. Maybe my expansion is just wrong .. :(

2. Feb 4, 2009

### Dick

The form of the expansion is correct. It should work.

3. Feb 4, 2009

### Staff: Mentor

The main idea is that the equation
$$\frac{A}{s^2} + \frac{B}{s} + \frac{Cs + D}{s^2 + 6s + 10} = \frac{10}{s^2(s^2 + 6s + 10)}$$
has to be true for any value of s except those that make one or more denominators vanish. If you pick four values of s you should get four equations in four unknowns, from which you should be able to get A, B, C, and D.

4. Feb 4, 2009

### rootX

Have found C?

C and B are related ...

5. Mar 12, 2009

### smalllittle

got it. thanks all