Can someone remind me which Binomial Expansion formula is used to expand:

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

Thanks in advance.

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- Jan 10th 2009, 02:59 AMSimplicityBinomial Expansion
Can someone remind me which Binomial Expansion formula is used to expand:

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

Thanks in advance. - Jan 10th 2009, 03:43 AMmr fantastic
- Jan 10th 2009, 03:53 AMHallsofIvy
If you really want to do it using the (generalized) binomial expansion, do it as $\displaystyle (a+ 1)^n$ with $\displaystyle a= x^2$ and n= -1.