The problem says to find the radii of convergence of these two functions:

$\displaystyle 2-\sqrt{1+x^2}$

$\displaystyle 1-\ln{(1+x^2)}$

But I am not sure how to do this. Could you just take the limit of each and set that to be less than 1? I am just not sure how to approach this problem. Thanks ahead of time for the help.