How do you get N(N+1) from N+1 + N + 1 + ... + N + 1 + N + 1?

Question

How does:

    1 +   2 + ... + N-1 +   N
 +  N + N-1 + ... +   2 +   1
  ---------------------------
 N+1 + N+1 + ... + N+1 + N+1

equal N(N + 1)? Shouldn't it be 4N + 4 or 4(N + 1)?

Answer 1

It is N(N + 1).

Because you have N number of (N+1) terms.