Hi everybody,

I am having some trouble with these questions and I'm not really sure where to start.

Find the term independant of $\displaystyle x$ in the expansion of:

$\displaystyle

(\frac{1}{3x} - \frac{3x^2}{2})^9$

Find the value of $\displaystyle n$ for which the coefficients of $\displaystyle x, x^2$ and $\displaystyle x^3$ in the expansion of $\displaystyle (1 + x)^n$ form three consecutive terms of an arithmetic series.

Thanks all.