- #1

- 442

- 0

When (1+ax)

^{n}is expanded as a series in expanding powers of x, the first three terms are 1 - 8x + 30x

^{2}

Calculate the values of a and n.

So, I think we need simultaneous equations and I managed to build the first one:

a*n = 8

My problem is however, that to construct the second equation I need to transform nCr in to something I can work with. I know it is something around

n(n-1)(n-2) / 2!

But I am not sure and I don't know how to work with these. Could anyone please help me?

Thanks!

Peter G.