the series is..

[(3^n)(x+4)^n]/(n^0.5)

did the ratio, ended up with

3(x+4)(n^.5)/(n+1)^.5

I got the interval of convergence correctly, but for the radius, the back of the book is saying 1/3 (when, what I'm having right now is 3x+12<1 ).

So my question is just.. how did they get the 1/3? Do numbers not count if they're not attached to variables or did I just make a mistake