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# binomial expansion help! watch

1. I dont understand what you do when you find when the expansion of a function is valid. I have gathered from examples that if it is:
(1-2x)^-1
valid for when 2x<1 so when x<1/2
but dont quite get it, just seeing the pattern from examples. The question I have is stating whether the series expansion i got (2-2x+10x^2) is valid for x=1/2. I thought you got when it is valid from the orginal function you expand?!?!
2. It's all about whether the series you get converges.

Sometimes you can expand the same expression in different ways, and you might choose the one that does the job.

I don't get what specific series you are working on.

(1-2x)^-1 starts to expand to 1 + (-1)(-2x) + (-1)(-2)(-2x)^2 / 2! + ....

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Updated: February 9, 2010
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