知乎，中文互联网高质量的问答社区和创作者聚集的原创内容平台，于 2011 年 1 月正式上线，以「让人们更好的分享知识、经验和见解，找到自己的解答」为品牌使命。

I am unsure how to go about doing this inverse product problem: The question says to find the value of each matrix expression where A and B are the invertible 3 x 3 ...

知乎，中文互联网高质量的问答社区和创作者聚集的原创内容平台，于 2011 年 1 月正式上线，以「让人们更好的分享知识、经验和见解，找到自己的解答」为品牌使命。

Jun 13, 2020 · Is there a formal proof for $(-1) \\times (-1) = 1$? It's a fundamental formula not only in arithmetic but also in the whole of math. Is there a proof for it or is it just assumed?

知乎，中文互联网高质量的问答社区和创作者聚集的原创内容平台，于 2011 年 1 月正式上线，以「让人们更好的分享知识、经验和见解，找到自己的解答」为品牌使命。

I am struggling to understand what the space $L^1$ is, and what it means for a function to be $L^1$. A friend told me that a function $f$ is $L^1$ if $\int_\mathbb {R} |f|$ is finite.

Feb 3, 2021 · Hi, welcome to Math SE! Can you show us the proof you're looking at? There are a lot of false proofs of this sort out there, typically involving division by 0, I would imagine that's probably the …

m = p 1 a 1 p 2 a 2 p 3 a 3 p n a n . 什么意思呢？ 它表示这样一个结论：对于任意的一个整数，你都能把它因数分解，而且结果是唯一的。 举个例子：1001只能被分解成7×11×13，而且你再也找不到除 …

May 11, 2015 · There are multiple ways of writing out a given complex number, or a number in general. Usually we reduce things to the "simplest" terms for display -- saying $0$ is a lot cleaner than saying …

May 15, 2013 · 這裡對陳浩的答案作補充，在定義完加法後要證明一個定理，即下文截圖的定理3，說明加法是 well-defined,well-defined的含義是指確實存在一個函數＋滿足（＊）式，若沒有此定 …