40 10 I need to format these numbers so that they form the sum 1, but they should keep their weight. In this specific case: 40 would become 0.80 10 would become 0.2 But if I have more values (like 40, 10, 25, 5 for example), I am really lost because I don't know the formula. 《道德经》是中国历史上最伟大的哲学名著之一，对传统哲学、科学、政治、宗教、商业、科技等众多领域产生了深刻影响和深远意义。据联合国教科文组织统计，《道德经》是除了《圣经》以外被译成外国文字发布量最多的文化名著。 《道德经》是春秋时期老子（李耳）的哲学作品，又称《道德. 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。 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。 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。 @turkeyhundt I don't like appealing to common sense results like this because it would lead one to believe that negative binomials (for example) aren't a thing due to the factorial function, and yet there is another definition that works (generalized version). I am after something a little more rigorous. Why is $1$ not considered a prime number? Or, why is the definition of prime numbers given for integers greater than $1$? 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 gimmick in the proof you've found. Here's a helpful link to get a sense for how to use MathJax. 比如，用质数组合得到数字6的唯一方法是2×3（顺序不重要，所以3×2算是同一种方法）。 然而，如果我们说1也算质数的话，那么得到6的方法就还有1×2×3和1×1×2×3，等等。 1的存在会破坏一切，对我们完全没有帮助。 所以我们必须弥补这个规则中的漏洞。.