## idku one year ago this can be a very good post...

1. freckles

the best post ever!

2. anonymous

yes, it can, but it isn't

3. Astrophysics

Seriously though, what's the question it shows it's in calculus 1 so it had me excited :P

4. idku

$$\Large \displaystyle\sum_{n=k}^{\infty}~f(n)=~?$$ (starting from any whole number k) we know: $$\Large \displaystyle\sum_{n=1}^{\infty}A_n=\frac{A_1}{1-r}$$ what is r in initial case? $$\Large \displaystyle r=\lim_{n\rightarrow \infty}\frac{a_{n+1}}{a_n}$$ so, $$\Large \displaystyle\sum_{n=k}^{\infty}~f(n)~=~\frac{A_k}{1-r}$$ $$\Large \displaystyle\sum_{n=k}^{\infty}~f(n)~=\frac{A_k}{\displaystyle1-\left(\lim_{n\rightarrow \infty}\frac{a_{n+1}}{a_n}\right)}$$ i don't even know why so many people are viewing.... (btw, just had to depart for a little)

5. idku

that is just a general thing that works for any f

6. idku

just a quick thought ... ))