Determine the radius of convergence of the following power series.
a) $\sum_{n=1}^{\infty}\frac{ x^{6n+2}}{(1+\frac{1}{n})^{n^2}}$
my attempts: by applying the ratio test i got $ \frac {a_n}{a_{n+1}}$ =$\frac{ x^{6n+2}}{(1+\frac{1}{n})^{n^2}}$.$\frac{(1+\frac{1}{n+1})^{(n+1)^2}}{ x^{6n+8}}$
i got $ \frac {a_n}{a_{n+1}}$ = $\frac{e}{x^6}$
now i don't know ...how to find the radius of convergence of given power series.....Pliz help me
thanks in advance