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.