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Binomial Theorem watch

1. Got a maths C2 exam on Monday and noticed something I hadn't been taught.

Reducing (a+b)^n to k(1+x)^n

Can anyone help explain this to me. Cheers

Also, on a past paper I could not get the following question

(1+ax)^n = 1 - 20x + 180x^2

the answer is n=10, a =-2

Any help appreciated

2. For the second question, post your working.
3. (Original post by notnek)

For the second question, post your working.
Thanks.

For the second question, I didn't have a clue. I tried to remove the (n over 1) and (n over 2) to no avail
4. From the binomial theorem:

So we have and .

Can you do it from here?
5. (Original post by notnek)
From the binomial theorem:

So we have and .

Can you do it from here?
Yes, I can thanks very much

Can I ask where you got . from?
6. (Original post by the stute)
Yes, I can thanks very much

Can I ask where you got . from?
The bit comes directly from the Binomial theorem. The = 180 bit is from the series that you gave. The co-efficient of the x^2 term is 180.
7. Aah, haven't been taught that part and its not on the syllabus anymore. The question was from 1 6 year paper, thats why Im unfamiliar. Cheers guys
8. (Original post by the stute)
Aah, haven't been taught that part and its not on the syllabus anymore. The question was from 1 6 year paper, thats why Im unfamiliar. Cheers guys
Which exam board/exam is this? Because I thought Binomial theorem was a standard C2 question

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