$\displaystyle \sum_{n=1}^{\infty} \frac{n}{7^n} (x + 4)^n $

I used the ratio test and after some cancellations, i get

$\displaystyle \sum_{n=1}^{\infty} \frac{n+1}{n} * \frac{x+4}{7}$

not sure if what i got so far is correct but i get stuck after i get to this part.

How do i finish this problem? thanks!