如要投诉，请到百度经验投诉中心，如要提出意见、建议， 请到百度经验管理吧反馈。 $begingroup$ Largely it is based on Conference, when one desires to determine the quantity $binom n 0 = frac n! n! 0! $ one example is. An intuitive way to take a look at it really is $n!$ counts the number of ways to rearrange $n$ unique objects https://bihlmayermedia-bilder.com/1-advent/