If f(x)=∑n=0∞anxnf(x) = \sum_{n=0}^{\infty} a_n x^nf(x)=∑n=0∞anxn has radius of convergence R=5R=5R=5, what is the radius of convergence of ∑n=0∞anx2n\sum_{n=0}^{\infty} a_n x^{2n}∑n=0∞anx2n?
5\sqrt{5}5
555
252525
1/51/51/5