does these series conv. or diver.?

1. to infiity n=1 $\displaystyle (arctan(n))/(n^3)$

im not sure where to start exactly, i was thinking Ratio or root test but im lost

2. to infinity n=1$\displaystyle ((-3)^n-1) /(4^n)

$

same as above, not sure

any help/tips would be greatly appreciated

Thanks