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# binomial expansion questions..

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1. is anyone willing to check these for me?
1) What is the coefficient of y^3 in the expansion of (1+y^6)
A: 20y^3
2) The coefficient of a^2b^5 in the expansion of (a+b)^7
A: 21a^2+b^5
3) the term a^2b^3 in the expansion of (a+2b)^5
A: 80a^2b^3
4) The expansion of (x+y)^8 contains the term
a- x^7y
b- 56x^2y^6
c-56x^3y^5
d-84x^4y^4
e-8y^8
I said c
Thanks very muchly xxxxx
2. Haven't done Binomial Expansion for a while, but I gave them a shot and got pretty much the same: Q1 is correct, Q2 is correct, (although I'm not sure why you've stuck a plus sign in your answer...), Q3 was the only one I differed on, but that's probably because I haven't done this stuff in a while - I don't know where 80 was from, but assume you're right..., and Q4 is correct.
3. yes.
well, yes, but that plus sign shouldn't be there.
yes.
yes.
4. thanks, i think the plus sign was a typo.
5. Happy to be of help!

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