The summation notation tells us
• Take the sum from i = 1 to i = 5
,• The formula is "9i"
So basically we plug in "1" into "i" of the formula, sum it up with plugging in "2" into i of the formula. Then sum it up with plugging in "3" into i of the formula and so on until 5.
Hence, it will be:
[tex]\begin{gathered} 9(1)+9(2)+9(3)+9(4)+9(5) \\ =9+18+27+36+45 \end{gathered}[/tex]THe third answer choice is right.