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Show that if n is an odd integer, then the number of ways to select an even number of elements from a set of n elements is equal to the number of ways to select an odd number of elements.

Can anybody help me?, i'm actually lost with this, i don't know how to proceed.

Viktor Vaughn
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  • When you have a combinatorial problem where two sets of things are equal in size, always look for a direct way of pairing one set with the other. If there is a trick, that is mainly what it is, and it is certainly the first thing to look for. Think carefully about this and it will help you to think about other similar (and rather more elusive) problems of a similar kind. – Mark Bennet Sep 11 '20 at 20:01
  • For odd $n$, selecting an even number of elements equals to removing an odd number of elements i.e. selecting an odd number of elements. – acat3 Sep 12 '20 at 04:02

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