Answer:
Summation notation is:
If you prefer it a little more simplified:
Step-by-step explanation:
First my favorite part, finding a pattern between the consecutive terms.
This is an arithmetic series because the terms are going up by 5 each time.
So arithmetic sequence, think linear equations:
x | y
1 -9
2 -4
3 1
4 6
..................
n 66
We are going to have to find that n but will will eventually...
The equation for a line in point slope form is where
is a point on the line and m is the slope.
We are already have the slope is 5 (the slope is the common difference in arithmetic sequence).
I'm going to use the first point (1,-9).
So the equation in point slope form is
Subtract 9 on both sides:
Now we need to know how many terms we are adding so what is x if y=66.
Add 9 on both sides:
Divide both sides by 5:
Add 1 on both sides:
We have 16 terms in this sequence where the 16th term is 66.
Summation notation is:
You could simplify the 5(x-1)-9.
Distribute: 5x-5-9
Add like terms: 5x-14