The Student Room Group

Binomial help please?

https://gyazo.com/d29056b8619a78d03213a28a1eafa0ce

For part 3.1 (a) I wrote: (x+6)(x+5)(x-1)(x-2)(x-3)(x-4) is that sufficient?
I'm not sure how you do part 3.1 (b) any help/guidance would be appreciated.

For part 3.2 (a) I got 3640. Is that correct? I did 15C12 . (2)^3 . x^13 .*. coefficient is 3640.

I'm completely lost on part 3.2 (b)? :cry:


Thanks in advance! :smile:
(edited 6 years ago)
Reply 1
Original post by XxKingSniprxX
https://gyazo.com/d29056b8619a78d03213a28a1eafa0ce

For part 3.1 (a) I wrote: (x+6)(x+5)(x-1)(x-2)(x-3)(x-4) is that sufficient?
I'm not sure how you do part 3.1 (b) any help/guidance would be appreciated.

For part 3.2 (a) I got 3640. Is that correct? I did 15C12 . (2)^3 . x^13 .*. coefficient is 3640.

I'm completely lost on part 3.2 (b)? :cry:


Thanks in advance! :smile:


3,1(b) the constant term will be the product of the roots and the x^5 term will be the sum. (Up to a + or -)
Reply 2
Original post by XxKingSniprxX
https://gyazo.com/d29056b8619a78d03213a28a1eafa0ce

For part 3.1 (a) I wrote: (x+6)(x+5)(x-1)(x-2)(x-3)(x-4) is that sufficient?
I'm not sure how you do part 3.1 (b) any help/guidance would be appreciated.

For part 3.2 (a) I got 3640. Is that correct? I did 15C12 . (2)^3 . x^13 .*. coefficient is 3640.

I'm completely lost on part 3.2 (b)? :cry:


Thanks in advance! :smile:


3.2(a) is correct.

3.2(b): what's the coefficient of x^n in (1 + x)^(2n)

What about the coefficient of x^n in (1+x)^n (1 + x)^n when you expand out each one of (1 + x)^n and then multiply them together. This will be a sum (the 1 from one bracket times the x^n in another + the x in one bracket times the x^(n-1) in the other + etc...

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