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.
plot 0.25 + 1.5 / (1 + exp(-0.01 * (x - 500))), x = 0..1000
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random
