Convergence of Geometric SeriesIn Probability, ex=∑n=0∞xnn!e^x = \sum\limits_{n=0}^{\infty} {x^n \over n!}ex=n=0∑∞n!xn ∑n=1∞an\sum\limits_{n=1}^{\infty} a^nn=1∑∞an converges if ∣a∣<1|a| < 1∣a∣<1.