I don't know if this is the correct thread as the titles can be so confusing, so I apologise If I've got this wrong.

Ok I have a few questions here and I've tried to solve them all myself unsuccessfully. I know it would take hours to finish them all, so could you at least provide me with a helpful tutorial as I'll have to go to bed now and these are due first thing tomorrow

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Finally,

5) When $\displaystyle (1+ax)^n$ is expanded as a series in asceding powers of x, the co-efficients of x and $\displaystyle x^2 $are -6 and 27 respectively. Find the values of a and n, the coefficient of $\displaystyle x^3 $and state the expressions for which the expansion is valid.

Thanks in advance for any replies.