Question

If n C5 = C7, then the value of n is ...​

Answer 1

n!/(5!*(n-5)!) = n!/(7!*(n-7)!)

Cancel terms, 7!/5! = (n-5)!/(n-7)!

(n-5)*(n-7)! = (n-5)! And 7*5! = 7!

Use it, 7 = n-5.

Therefore n=12.

n = 7+5 = 5.

n=12.

So the value of n is 12