Uploaded February 2026 | Updated September 2026, 2 weeks ago

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We will discuss why 0 factorial is equal to 1, i.e. 0!=1. In fact, once you see the pattern, you will see it immediately. This question is from Reddit r/learnmath.
reddit.com/r/learnmath/s/lDwRmPBTbW
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#math #algebra #mathtutorials

0:00 Zero factorial, why 0!=1
3:17 How about (-1)! = ?
4:29 Meaning of factorial and why we need it