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# C2 bionomial expansion watch

1. I am stuck on this question:
given that (1+x)^n = 1 + 12x + x^2 find the value of a

Does n= 2 ? Im not sure on how to do this question
2. (Original post by Alex-Torres)
I am stuck on this question:
given that (1+x)^n = 1 + 12x + x^2 find the value of a

Does n= 2 ? Im not sure on how to do this question
Where's a being defined? all I can see are n's and x's, unless you mean (1+ax) but still then its a bit cryptic. And no, n does not equal 2 since using the laws of expansion
3. (Original post by Alex-Torres)
I am stuck on this question:
given that (1+x)^n = 1 + 12x + x^2 find the value of a

Does n= 2 ? Im not sure on how to do this question
There isn't an 'a' in the question?

( 1+ax )n ?
5. (Original post by Robbie242)
Where's a being defined? all I can see are n's and x's, unless you mean (1+ax) but still then its a bit cryptic. And no, n does not equal 2 since using the laws of expansion
(Original post by Felix Felicis)
There isn't an 'a' in the question?
(Original post by the bear)

( 1+ax )n ?
Sorry. Given that (1+x)^n = 1 + 12x + ax^2, find the value of a.
6. (Original post by Alex-Torres)
Sorry. Given that (1+x)^n = 1 + 12x + ax^2, find the value of a.
Notice that from earlier the 2nd term divide by x, and we have n=12, I'm sure you know how to solve for a now

Spoiler:
Show
Find the x^2 term in the expansion and set it equal to ax^2
7. well the x2 term is given by

{n( n-1 )/2! }x2
8. (Original post by Alex-Torres)
Sorry. Given that (1+x)^n = 1 + 12x + ax^2, find the value of a.
Should this be or does it stop at the x^2 term?
9. (Original post by Felix Felicis)
Should this be or does it stop at the x^2 term?
It stops at the ax^2
10. (Original post by Alex-Torres)
It stops at the ax^2
That can't be right? By the information you've given me I've deduced that n=12, it can't be untrue as its part of the standard expansion, I think it goes on for longer otherwise people would just say n=2 herp derp which isn't true for the 2nd term
11. (Original post by Robbie242)
Notice that from earlier the 2nd term divide by x, and we have n=12, I'm sure you know how to solve for a now

Spoiler:
Show
Find the x^2 term in the expansion and set it equal to ax^2
I got 66?
Attached Images

12. (Original post by Alex-Torres)
I got 66?
That is correct, now set it equal to ax^2 and solve for a also a quicker way for terms like this if in the form
13. (Original post by Robbie242)
That is correct, now set it equal to ax^2 and solve for a also a quicker way for terms like this if in the form
Doesnt a just equal 66 and thats the end of the question?
14. (Original post by Alex-Torres)
Doesnt a just equal 66 and thats the end of the question?
and that is indeed, try not to forget if you expand up to a term to leave +.... some examiners may be very picky about this
15. (Original post by Robbie242)
and that is indeed, try not to forget if you expand up to a term to leave +.... some examiners may be very picky about this
Thanks!
Do you know where I went wrong in this question?
16. (Original post by Alex-Torres)
Thanks!
Do you know where I went wrong in this question?
Try be more careful in your workings and re-expand, one of the terms I got was to be -45, just re-expand more carefully
17. (Original post by Robbie242)
Try be more careful in your workings and re-expand, one of the terms I got was to be -45, just re-expand more carefully
Could you please take a picture of your working, as I can't see how you got that answer?
18. (Original post by Alex-Torres)
Could you please take a picture of your working, as I can't see how you got that answer?
Sure after dinner if your still stuck, will be like 10 mins
19. (Original post by Alex-Torres)
Thanks!
Do you know where I went wrong in this question?
Man, root3^5 is root3 x root3 x root3 x root3 x root 3... Which gives root 243 which is 9root 3.
And similarly for the rest!
20. (Original post by Robbie242)
Sure after dinner if your still stuck, will be like 10 mins
Im OK now, but thanks anyway! And the above poster

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