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.
1 - 5*0.8^x + 10*0.6^x - 10*0.4^x + 5*0.2^x for x=1,2,...,21
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random