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，

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@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 factori

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

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，

Apr 25, 2013 · The examples given with base 10 and 2 in the question are positional bases. In a positional base 1, you only got one digit, with no value: 0. All positions will hav

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，

Binomial expansion of $ (1-x)^n$ Ask Question Asked 11 years, 7 months ago Modified 5 years, 1 month ago Viewed 250k times

Note that $$\frac {1} {1+x}=\sum_ {n \ge 0} (-1)^nx^n$$ Integrating both sides gives you \begin {align} \ln (1+x) &=\sum_ {n \ge 0}\frac { (-1)^nx^ {n+1}} {n+1}\\ &=x ...

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