# Math Help - Binominal help

1. ## Binominal help

n
c2 = 28

how do i find what is n?

2. $C_n^2=\frac{n(n-1)}{2}$

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

Now solve the quadratic and choose the positive integer solution.