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.
erf ((x-850)/(100*sqrt(2))) = -0.9
erf ((x-850)/(100*sqrt(2))) = -0.9
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random
