Series Solutions · Hard problem

Equation A is $x^2y'' + y' + y = 0$, with its only singular point at $x=0$. Equation B is $(x^2+4)y'' + y = 0$, with singular points at $\pm 2i$. Both are expanded about $x_0 = 1$. By how much does the guaranteed radius of convergence for Equation B exceed that for Equation A? Give an exact answer.