知乎，让每一次点击都充满意义 —— 欢迎来到知乎，发现问题背后的世界。 natural This kind of operate represents a partial perform on naturals, the place the proof of even (n) could be noticed as being a precondition. From the Cambridge English Corpus There isn't any real difference between the standard first-purchase objects on the mathematical discourse - for instance https://elliotwfkpr.blazingblog.com/35734433/herbal-remedies-for-dogs-can-be-fun-for-anyone