http://www.bing.com:80/search?q=1.5L+O2+FiO2Search resultshttp://www.bing.com:80/s/a/rsslogo.gifhttp://www.bing.com:80/search?q=1.5L+O2+FiO2Copyright © 2026 Microsoft. All rights reserved. These XML results may not be used, reproduced or transmitted in any manner or for any purpose other than rendering Bing results within an RSS aggregator for your personal, non-commercial use. Any other use of these results requires express written permission from Microsoft Corporation. By accessing this web page or using these results in any manner whatsoever, you agree to be bound by the foregoing restrictions.https://www.zhihu.com/question/46263998红线是n-1到n的割线，绿线是n处的切线 图像上显然，割线的斜率大于切线的斜率。 所以我们有割线的斜率 \dfrac {\ln \left ( n\right) -\ln \left ( n-1\right) } {n-\left ( n-1\right) } 大于切线的斜率 \left ( \ln n\right) '=\dfrac {1} {n} 。 我们有 \ln n-\ln \left ( n-1\right) >\dfrac {1} {n} 我们累加 \sum \left ( \ln n-\ln \left ( n-1\right ...Wed, 15 Apr 2026 18:02:00 GMThttps://www.zhihu.com/selection/知乎是一个中文互联网高质量问答社区和创作者聚集的原创内容平台，提供知识共享、互动交流和个人成长机会。Wed, 15 Apr 2026 10:09:00 GMThttps://www.zhihu.com/question/276303327我们可以从数学上证明 1+1=2，但是如何定义 1 是什么。如果说是 0 的后继数，那又如何定义 0 呢？Wed, 15 Apr 2026 15:24:00 GMThttps://math.stackexchange.com/questions/304422/formal-proof-for-1-times-1-1Is 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?Fri, 10 Apr 2026 12:10:00 GMThttps://www.zhihu.com/question/19952889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。Mon, 13 Apr 2026 15:20:00 GMThttps://www.zhihu.com/?lang=zh-Hant知乎是一个中文互联网高质量问答社区，提供知识分享、经验交流和见解探讨的平台。Sun, 12 Apr 2026 21:19:00 GMThttps://math.stackexchange.com/questions/1901716/false-proof-of-1-11 Indeed what you are proving is that in the complex numbers you don't have (in general) $$\sqrt {xy}=\sqrt {x}\sqrt {y}$$ Because you find a counterexample.Mon, 13 Apr 2026 13:11:00 GMThttps://math.stackexchange.com/questions/120/why-is-1-not-a-prime-number50 actually 1 was considered a prime number until the beginning of 20th century. Unique factorization was a driving force beneath its changing of status, since it's formulation is quickier if 1 is not considered a prime; but I think that group theory was the other force.Sun, 12 Apr 2026 00:47:00 GMThttps://www.zhihu.com/question/629546895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。知乎凭借认真、专业、友善的社区氛围、独特的产品机制以及结构化和易获得的优质内容，聚集了中文互联网科技、商业、影视 ...Mon, 13 Apr 2026 01:08:00 GMThttps://math.stackexchange.com/questions/1277038/why-is-1-i-equal-to-iThere 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 $1-1$ for example. The complex numbers are a field. This means that every non-$0$ element has a multiplicative inverse, and that inverse is unique. While $1/i = i^ {-1}$ is true (pretty much by definition ...Mon, 13 Apr 2026 01:22:00 GMT