How is summation notation used?

Question

I know the summation notation operator is Σ; but how do you use it to find the sum of a series?

Answer 1

You use the notation operator to indicate that the terms that are evaluated by the variable term cited are being summed. There should be a starting and ending boundary pt on the notation.

For example, if you had SUM(1/(n-1)!) from 2 to 7, this would indicate
1+ 1/2!+ 1 /3!+ 1/4!+ 1/5!+ 1/6!

Answer 2

The summation of 1, 2, and 4 is 1 + 2 + 4 = 7. The sum is 7. Since addition is associative, it does not matter whether we interpret "1 + 2 + 4" as (1 + 2) + 4 or as 1 + (2 + 4); the result is the same, so parentheses are usually omitted in a sum. Finite addition is also commutative, so the order in which the numbers are written does not affect its sum.

Answer 3

To find the sum of numbers from 1 to n:
n
Σxi
i = 1
Where xi are the numbers from a list. Imagine the "i" ,and the numbers below, as a subscripts to the x variable.
Suppose we have a list, x1= 4, x2 = 2, x3 = 5, and x4 = 1. Then the summation would be shown as:
4
Σxi = 12
i = 1