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.
解 n! = 720 。（答： n = 6 。）
解 n! = 720 。（答： n = 6 。）
Natural Language
Math Input
Extended Keyboard
