A Question Regarding Limitations

33 Views Asked by At

How many ways can we calculate these limitations about factorial? $$1+a+\frac{a^2}{2!}+\frac{a^3}{3!}+...+\frac{a^n}{n!}\\ \frac{1}{2!}-\frac{1}{3!}+\frac{1}{4!}-+...+\frac{(-1)^n}{n!}$$ I met this kind of limitations when I dealt with Poisson random variables and don't know how to solve them.

1

There are 1 best solutions below

2
On BEST ANSWER

The first converges to $e^a$ (it is the exponential series) and the latter is the special case where $a=-1$, so converges to $e^{-1}$.