Hi all,

I had two questions

1. $\displaystyle \sum ^{\infty}_{i=1} \frac{1}{\left(i-1\right)!} \frac{d}{d\lambda} \left(\lambda^{i}\right)= \frac{d}{d\lambda} \sum ^{\infty}_{i=1} \frac{1}{\left(i-1\right)!} \lambda^{i} $

2. $\displaystyle \sum^{\infty}_{x=1} x r^{x} = \frac{r}{\left(1-r\right)^{2}}$

why are 1 and 2 true

For the first I think it has to do with the radius of convergence.

Can someone help to prove this,

Thank you very much