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# Binomial Expansion C1 Help ! watch

1. Hi Ive got this question to do for homework and I cant seem to do it !

Find: the value of the term in the expansion of (x-1/x)^8 which is independent of x

the answer is 70 by the way

Thanks
2. Are you sure it is 70?
3. Here's one way to do it which makes it a bit easier:

Then

Then notice that the terms independent of x will be the coefficient of the term in the expansion of .
4. (Original post by DeanK2)
Are you sure it is 70?
Yes, it is.
5. (Original post by Simba)
Yes, it is.
yeah - just did the choose thing on the calculator,I suck at mental maths

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