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# Binomial Expansion watch

1. xx
2. (Original post by CarissaG)
How to expand 1/8 (e^x - e^-x)^3 using binomial expansion?
Is that supposed to be

?

Just expand the numerator using the usual binomial formula for and then simplify.
3. You may recognise

Write down the first few terms of the expansion of from your formula book and cube it ignoring terms you don't need.
4. Well the question asks for a binomial expansion, not a Taylor expansion in .

If you are happy with

You can always write

Then putting you get

Simplify this and then substitute the result back into

.

Simplify and collect together terms. The end result is expressible in terms of and .

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Updated: January 21, 2014
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