# Proving a perfect square with factorials

Coldie
The tex seems to be showing different problems than the ones I'm typing... maybe it's just me, but if what I'm talking about doesn't seem to make any sense, please quote my message to see what I've actually typed in the tex tags.

If n is a positive integer and n > 1, prove that nC2 + (n-1)C2 is a perfect square.

Now, expanded, this is what they look like...

[TEX]\frac{n!}{2!(n-2)!} + \frac{(n-1)!}{2!(n-3)!}[/TEX]

I'm not sure whether to multiply by the denominators or whether I'm simply supposed to try to simplify each one on its own, or a combination of the two. Moreover, I'm certain I'll still have at least one factorial left when I'm through, and how can I prove that any function with a factorial in it is a perfect square? Could someone give me a nudge in the right direction?