Hi

The question given is

Prove by mathematical induction that

$\displaystyle \frac{1}{3} + \frac{2}{3^2} + \frac{3}{3^3} + \frac{n}{3^n} = \frac{1}{4}(3-\frac{2n + 3}{3^n})$

I've spent quite a bit of time on this, playing around with it, but can't seem to make any head-way. If anyone can give any hints or tips at all i'd be rather grateful.

-Dave