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 (-5)^n / 8^(2n),n = 2 to inf
sum (-5)^n / 8^(2n),n = 2 to inf
Natural Language
Math Input
Extended Keyboard
