# Series of partial sums

1. Nov 8, 2016

### gkamal

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

2. Relevant equations

an= bn - bn+1 which is already in the problem

3. The attempt at a solution

i did partial fractions but then i got stuck at

16/12 [4n-5] - 16/12 [4n+7] that part about bn confuses me please someone explain in detail

2. Nov 8, 2016

### Staff: Mentor

Where's the equation you're working with?
Starting from $\frac{16}{16n^2 + 8n - 35} = \frac{A}{4n - 5} + \frac{B}{4n + 7}$, multiply both sides by $16n^2 + 8n - 35$ to clear out all of the denominators. Then solve for the constants A and B.

3. Nov 8, 2016

### gkamal

i did and i get 16/12 for A and - 16/12 for B as i indicated above the problem is what is the next step

4. Nov 9, 2016

### vela

Staff Emeritus
I think there's a typo in the problem. It should say $a_n = b_n - b_{n+3}$.