Question

Write the sum using summation notation, assuming the suggested pattern continues.

-3 + 6 + 15 + 24 + ... + 132

Answer 1

Lets do this.

can you tell me the difference ?

Answer 2

oops the common ratio

Answer 3

the common ratio is ?

Answer 4

=9?

Answer 5

Yes, it is difference

Answer 6

The sequence confused me, sorry.

Yes d=9

Answer 7

How many terms ?

Answer 8

\(\large\color{blue}{ a_n=a_1+d(n-1)}\) solving for n

\(\large\color{blue}{ 132=-3+9(n-1)}\)

\(\large\color{blue}{ n=?}\)

Answer 9

n=23?

Answer 10

15

Answer 11

my bad

Answer 12

add 3 to both sides
divide both sides by 9
add 1 to both sides

it is not 23

Answer 13

15 is `n-1`

and `n` = ?

Answer 14

16 lol

Answer 15

Yes

Answer 16

So a1=3
d=9
number of terms =16

Answer 17

Fill in the Σ (alt code for Σ, is 2 2 8 )

Answer 18

\[\LARGE \sum_{index}^{number~~of~~terms}~~(equation)\]

Answer 19

index is what you start putting in for "n" into the equation to get whatever term.

Answer 20

Go, shoot !

Answer 21

15
Σ-27n
n=0

Answer 22

i tried :/

Answer 23

or is it -3+9n?

Answer 24

instead of multiplying

Answer 25

would \[\sum_{n=0}^{15}~~(-3+9n)\]suffice ?

Answer 26

yes, that was my second guess

Answer 27

i didn't know which one

Answer 28

Yes:)

Answer 29

I want to outline what we did

Answer 30

go for it

Answer 31

1) Found the difference
2) Found the number of term
3) Found a sum notation

would you be able to do it on your own in the future ?

Answer 32

2) ... *terms

Answer 33

i think so

Answer 34

Good luck with your next question.... !

Answer 35

wait, is there something i did wrong?