Series Converge Value

Summation from 0 to infinity of (x+9)^n / 8^n.

Find the values of x for which the series converges.

Find the sum of the series for those values of x.

I didn't know how to do this one. I'm pretty lousy as the series/sequence stuff. I rewrote it as [(x+9)/8]^n to make it a geometric series but I don't think that's correct.

I'm not getting the right answer for the second part.

a=(x+9)/8 , r=(x+9)/8 so I used the a/(1-r) and then multiplied by 8 and got:

(x+9) / [8-(x+9)] which goes to (x+9) / (-x-1)

Edit: Nevermind... it's summation 0 to infinity and I kept doing 1. I got it. Thanks!