n

c2 = 28

how do i find what is n?

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- Sep 18th 2009, 02:00 AMhelloyingBinominal help
n

c2 = 28

how do i find what is n?

- Sep 18th 2009, 02:04 AMred_dog
$\displaystyle C_n^2=\frac{n(n-1)}{2}$

Then $\displaystyle \frac{n(n-1)}{2}=28\Rightarrow n^2-n-56=0$

Now solve the quadratic and choose the positive integer solution.