given a collection of 2n objects,n of which are identical and n of which are all distinct,howmany different subcollection of n objects are possible?有一系列2N的东西 N个事一样的 N个事不一样的 有多少个集合？　　　　答案

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given a collection of 2n objects,n of which are identical and n of which are all distinct,howmany different subcollection of n objects are possible?有一系列2N的东西 N个事一样的 N个事不一样的 有多少个集合？　　　　答案

given a collection of 2n objects,n of which are identical and n of which are all distinct,howmany different subcollection of n objects are possible?有一系列2N的东西 N个事一样的 N个事不一样的 有多少个集合？　　　　答案
given a collection of 2n objects,n of which are identical and n of which are all distinct,how
many different subcollection of n objects are possible?有一系列2N的东西 N个事一样的 N个事不一样的 有多少个集合？　　　　答案是NC0＋　Nc1 + ......+Ncn

given a collection of 2n objects,n of which are identical and n of which are all distinct,howmany different subcollection of n objects are possible?有一系列2N的东西 N个事一样的 N个事不一样的 有多少个集合？　　　　答案
如果该集合中只有一个,那么就有N+1个集合,如果有两个,则有两种1是在n个一样的中选一个和不一样的中选一个,则有n中,2,就是两个全是不一样的,就只有在那N个不一样的东西中选择,就有C20,2,如果有三个,也有两种,一是在不一样中的选择两个,一样的一个,就有C20,2种,第二就是全在不一样事物中选择3个,就有C20,3种,以此类推,就会得到答案的、谢谢,

a collection of show that,given any sequence of n integers,x1,x2,x3.xn some consecutive collection has a sum dividible by n a given COLLECTION collection a books collection 和a book collection哪个对 a small sports collection 侞题~ a great sports collection是什么意思? I have a sports collection They have a great collection. a matter/waste/collection of a ball collection什么意思? 英文翻译3Quality control (QC) is the collection of methods and techniques for ensuring that a product or service is produced and delivered according to given requirements. This includes the development of specifications and standards, performance 翻译：Ed has a great sports collection. a great sports collection什么意思? have a sports collection的汉语意思 He have a great sports collection.改错 Ed Smith has a great sports collection.