Possible Duplicate:
How can I evaluate $\sum_{n=1}^\infty \frac{2n}{3^{n+1}}$
please help me with this $$\sum\limits_{k=0}^{\infty}\frac{k}{3^k}$$
I need just a hint, not a full answer. Thanks!
Possible Duplicate:
How can I evaluate $\sum_{n=1}^\infty \frac{2n}{3^{n+1}}$
please help me with this $$\sum\limits_{k=0}^{\infty}\frac{k}{3^k}$$
I need just a hint, not a full answer. Thanks!