Please help me with this problem involving the use of the Ratio Test to determine the interval of convergence.

6. Use the ratio test to explicitly determine the interval of convergence of the Taylor series. 2 (a) (-1) k k k=1 2 (b) E K! *=0 2 (c) (-1) ka2k k=0 (2k)! 2 (d) *2 ( 2 + 1) k k=0 2 (e) (20 - 4) K 2k k=0