Find the radius of convergence for ∑n=1∞4nn!(2n)!xn\sum_{n=1}^{\infty} \frac{4^n n! }{(2n)!} x^n∑n=1∞(2n)!4nn!xn using the ratio test.
R=1R = 1R=1
R=2R = 2R=2
R=∞R = \inftyR=∞
R=4R = 4R=4