Write the sum using sigma notation: 3+6 + 9 + 12. What goes above the sigma and what is to the right. I know n = 1 goes under the sigma.

Answer 1

The n values above and below the sigma sign depends on the formula that's used. The easiest formula for the series you gave is 3n... so the values could come from 3(1) + 3(2) + 3(3) + 3(4).

So the number above the sigma sign would be 4; the formula to the right would be 3n; and the expression below the sigma sign would be n = 1.