Question

(2n)!/n! = ?

Answer 1

\[(2n)! = 2n*(2n-1)*(2n-2)\cdots (n+1)*n!\]

Answer 2

so when you divide, the n! will cancel out, leaving only:
\[2n*(2n-1)*(2n-2)\cdots (n+2)(n+1)\]

Answer 3

Which you may write as \[\Pi_{k=n+1}^{2n} k\]

if you are feeling lazy:-)