Answer:
-35
Explanation:
Knowledge Needed
This notation is called sigma notation (or summation). It is used later on in Calculus too.
The number on top of the sigma sign is called the top index.
The number on bottom of the sigma sign is called the lower index.
To the right of the sigma sign is an expression.
I will give you an example to help.
3
Σ n^2
n = 1
To start, look at the bottom number. Then, plug all numbers from the lower index to the top index (including the top index) into the expression.
n^2
(1) ^ 2
(2) ^ 2
(3) ^ 2
We stop at 3 because 3 is the top index.
Simplify.
1 ^ 2 = 1
2 ^ 2 = 4
3 ^ 2 = 9
Add the numbers.
9 + 4 + 1
14
The answer is 14.
Question
Start at 1 and go to 5.
-2n-1
-2(1)-1
-2(2)-1
-2(3)-1
-2(4)-1
-2(5)-1
Stop at the 5, the top index.
Simplify.
-2 - 1 = -3
-4 - 1 = -5
-6 - 1 = -7
-8 - 1 = -9
-10 - 1 = -11
Add.
-3 + -5 + -7 + -9 + -11
-35