Binomial expansion of a function with x raised to a power

AI Thread Summary
To binomial expand the function 1/(1-x²), the series can be expressed as 1 + (-1)(-x²) + (-1)(-2)(-x²)²/2! + (-1)(-2)(-3)(-x²)³/3! and so on. This expansion is correct, and the coefficients follow a pattern based on factorials and alternating signs. Understanding this pattern will aid in expanding similar functions like ∏(1/(1-x^i)) for i up to 6. The discussion emphasizes recognizing the coefficients in the expansion and their relationship to the binomial series. Mastering this technique will facilitate further calculations involving binomial expansions.
Dixanadu
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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!
 
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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.
 
Wait, wait- don't tell me. I'm still working on it!
 
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