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# C2 - Binomial Expansion watch

1. Question:

When is expanded the coefficient of

Given that , use this information to find the value of the constant .

So far, I worked out (although I'm most likely wrong) that -

the coefficient in terms of is equal to
and therefore:

As far as I know the quadratic isn't solveable by simple factorising (C2), so I'm presuming I've gone wrong somewhere - does anyone know where?
2. (Original post by Wilko94)
So far, I worked out (although I'm most likely wrong) that -

the coefficient in terms of is equal to
and therefore:
Close, but don't forget it's "-3x" that you're squaring, which doesn't give -3x^2.

Hope that wasn't too cryptic.

Edit: And as Ben121 observed, you've not multplied and divided into the 54 correctly.
3. I'm not entirely sure you should have that 9 there. You have made a mistake when writing the quadratic.
4. (Original post by ghostwalker)
Close, but don't forget it's "-3x" that you're squaring, which doesn't give -3x^2.

Hope that wasn't too cryptic.

So would this be correct?

5. (Original post by Wilko94)

Yep.
6. (Original post by ghostwalker)
Yep.
Thank you very much to the both of you.

Ben121 you have been repped, ghostwalker when I try to rep you, I get the message -

Please rate some other members before rating this member again.
You've probably helped me already with my Maths as I always rep the person that helps me, and I tend to be asking for help frequently. Thank you very much anyway!

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Updated: April 2, 2011
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