Uh oh! Wolfram|Alpha doesn't run without JavaScript.
Please enable JavaScript. If you don't know how, you can find instructions
here
.
Once you've done that, refresh this page to start using Wolfram|Alpha.
\sum_{n=0}^{\infty} (4/5)^(n+1)
\sum_{n=0}^{\infty} (4/5)^(n+1)
Natural Language
Math Input
Extended Keyboard
