# Maclaurin series

1. May 21, 2007

### Kuno

1. The problem statement, all variables and given/known data
find $$a_{n}$$ for $$f(x)\ =\ \frac{1}{1+3x}$$

3. The attempt at a solution
I got:
f(0) = 1
f'(0) = -3
f''(0) = 9

The answer I ended up with was:
$$a_{n} \ = \ {(-1)}^n\frac{3^n}{n!}$$

However, the answer in the back of my book has the same answer except it's not divided by n!.

2. May 22, 2007

### truewt

the n! is cancelled out somehow. Recheck your workings.

Hint: Find f^n(x). I don't know what's the notation for the nth derivative of f(x)

3. May 22, 2007

### Kuno

Okay I see it now, thanks.

4. May 22, 2007

### truewt

you're welcome :)