Chu vandermonde identity states that ${s+t \choose n}=\sum_{k=0}^n {s \choose k}{t \choose n-k} $
Now how to prove that this identity is a discrete form of beta integral?
i see as a starting point to rewrite this identity for n+1 by replacing n by n+1 , then what? any help? since after writing that i seem to be getting a very crude expression that leads me no where.