A question about summation notation in series. Could someone explain why the answers in the attached image are correct? For the left question, the top two choices seem to be the exact same thing, so I do not understand why one is correct while the other is not. For the right question, why is the answer (4n+4)? When the bottom limit is the 0th term, I thought you were supposed to replace the n in the equation with (n-1), which would make it (4n-4).