Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.
Use induction to prove that for a finite set A of cardinality n, there are n(n+1)/2 distinct 2-element subsets of A. ?
i meant n-1
- az_lenderLv 73 months ago
Let's start with a set A that has only two elements. Then
n(n+1)/2 = 2*3/2 = 3.
And hence, your proposition is obviously false. There is only one 2-element subset of A.
I think you should've said n(n-1)/2.