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.
4 * 5 矩阵有多少元素？（答： 20 。）
4 * 5 矩阵有多少元素？（答： 20 。）
Natural Language
Math Input
Extended Keyboard
