The answer is 33. Take each value of i individually (the index of summation) and plug it in for i in the function. The first value you get when you plug in i = 1 is 3; the value you get when you plug in i = 2 is -6; the value you get when you plug in i = 3 is 12; the value you get when you plug in i = 4 is -24; the value you get when you plug in i = 5 is 48. Adding 3 + (-6) + 12 + (-24) + 48 = 33