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

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.