C2- Binomial expansion

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.

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.

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 $(1+ax)^{16}$.

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.

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.