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# Binomial expansion

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Why bother with a post grad? Are they even worth it? Have your say! 26-10-2016
1. So I need to expand (1-x+x^2)^1/2 up to x^3 but the answer I found is not what's in the book.

I found 1-(1/2)x+(3/8)x^2+(3/16)x^3 but in the back of the book it states that the correct answer is 1-(1/2)x+(5/8)x^2-(5/8)x^3 .... where did I go wrong?
2. (Original post by irenee)
So I need to expand (1-x+x^2)^1/2 up to x^3 but the answer I found is not what's in the book.

I found 1-(1/2)x+(3/8)x^2+(3/16)x^3 but in the back of the book it states that the correct answer is 1-(1/2)x+(5/8)x^2-(5/8)x^3 .... where did I go wrong?
Well clearly you went wrong on your third term onwards. Show some working before asking that. But that aside, I checked with Wolfram Alpha and it agrees with you.

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