If C(n,2)=6, then n=?

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Science & Mathematics by Anonymous 2018-06-19 07:33:59

Social Science

If C(n,2)=6, then n=?

4 answers

Anonymous

nC2 = n!/[(n-2)!2!] = n(n-1)/2. We are told that nC2 = 6. Then n(n-1) = 12 and n = 4.
Anonymous

nC2=6 => n(n-1)/2=6 => n^2-n-12=0 => (n+3)(n-4)=0 => n=-3 or 4 Ans. n=-3 or n=4
Anonymous

https://www.wolframalpha.com/input/?i=C(...
Anonymous

n!/(n-2)! = 12 n(n-1) = 12 n^2-n-12 = 0 (n-4)(n+3) = 0 n = 4