Which of the following is equivalent to ∑n=0∞2nn!xn\sum_{n=0}^{\infty} \frac{2^n}{n!} x^n∑n=0∞n!2nxn?
exe^xex
e2xe^{2x}e2x
2ex2e^x2ex
ex+2e^{x+2}ex+2