C2- Binomial expansion Watch

Super199
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I can normally do questions to do with binomial expansion but can't seem to figure this one out. Any help would be appreciated. Part A is where I am stuck, part b shouldn't be too much of a problem if I know the value of a.
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Mr M
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(Original post by Super199)
I can normally do questions to do with binomial expansion but can't seem to figure this one out. Any help would be appreciated. Part A is where I am stuck, part b shouldn't be too much of a problem if I know the value of a.
The binomial expansion is given in your formula book. Write down the first few terms and equate coefficients.
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Super199
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(Original post by Mr M)
The binomial expansion is given in your formula book. Write down the first few terms and equate coefficients.
Am I on the right lines? If so, I am not sure what to do next
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Mr M
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(Original post by Super199)
Am I on the right lines? If so, I am not sure what to do next
They were just expecting you to write \displaystyle 1+nax+\frac{n(n-1)a^2x^2}{2}=1-24x+270x^2

Edit: Didn't realise this was Core 2. Use the value n = 16 provided.
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Super199
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(Original post by Mr M)
They were just expecting you to write \displaystyle 1+nax+\frac{n(n-1)a^2x^2}{2}=1-24x+270x^2

Edit: Didn't realise this was Core 2. Use the value n = 16 provided.
Using what you said can I make a substitution for a? So a=-24/n.
Then sub that into n(n-1)a^2/2=270? Is that the way you are supposed to do it?
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Mr M
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(Original post by Super199)
Using what you said can I make a substitution for a? So a=-24/n.
Then sub that into n(n-1)a^2/2=270? Is that the way you are supposed to do it?
That's the A2 way to do it. You are just expected to write down the first 3 terms of the expansion of (1+ax)^{16}.
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Super199
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(Original post by Mr M)
That's the A2 way to do it. You are just expected to write down the first 3 terms of the expansion of (1+ax)^{16}.
ah right that is a lot simpler. Thanks
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ThatPerson
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(Original post by Mr M)
They were just expecting you to write \displaystyle 1+nax+\frac{n(n-1)a^2x^2}{2}=1-24x+270x^2

Edit: Didn't realise this was Core 2. Use the value n = 16 provided.
Isn't the (1+x)^n expansion in C2? It's mentioned in the textbook & the spec.
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Mr M
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(Original post by ThatPerson)
Isn't the (1+x)^n expansion in C2? It's mentioned in the textbook & the spec.
Not in the OCR specification I'm used to. Others may differ.
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Super199
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(Original post by ThatPerson)
Isn't the (1+x)^n expansion in C2? It's mentioned in the textbook & the spec.
It is, I've never used it before. I asked my teacher and he said you can just use whatever method you prefer for AS anyway. Guess I will have to look into it a bit more.
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Mr M
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(Original post by Super199)
It is, I've never used it before. I asked my teacher and he said you can just use whatever method you prefer for AS anyway. Guess I will have to look into it a bit more.
They have provided the value 16 so that you can use it if you choose to.
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Legal drugdealer
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so after you get a do you plug it back into the first three terms?
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