# Binomial expansion of a function with x raised to a power

1. Oct 6, 2013

Hey guys.

So I need to know how to Binomial expand the following function
$\frac{1}{(1-x^{2})}$.

I need this because I have to work out $\prod^{∞}_{i=1}$$\frac{1}{(1-x^{i})}$ for i up to 6. But I have to do it with Binomial expansion. If i can learn how to do $\frac{1}{(1-x^{2})}$ then the rest of the powers should be the same.

I was under the impression that $\frac{1}{(1-x^{2})}$ can be binomial expanded as

$1+(-1)(-x^{2})+(-1)(-2)\frac{(-x^{2})^{2}}{2!}+(-1)(-2)(-3)\frac{(-x^{2})^{3}}{3!}+...$

Is that correct?

Thanks guys!

2. Oct 6, 2013

3. Oct 6, 2013

### Office_Shredder

Staff Emeritus
This is correct, and you probably want to observe that
(-1)/1! = -1
(-1)(-2)/2! = 1
(-1)(-2)(-3)/3! = -1

and you can probably guess the pattern as you continue.

4. Oct 7, 2013

### HallsofIvy

Staff Emeritus
Wait, wait- don't tell me. I'm still working on it!