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

-4 + 5 + 14 + 23 + ... + 131

Question

Write the sum using summation notation, assuming the suggested pattern continues.

-4 + 5 + 14 + 23 + ... + 131

anonymous · Answer

@welshfella

anonymous · Answer

Do you notice a pattern?

anonymous · Answer

they go up by 9

anonymous · Answer

what does the question want you to answer

anonymous · Answer

to write summation notation for the sequence, filling out $$\sum_{?}^{?} $$

anonymous · Answer

sorry i can't help you there :(

anonymous · Answer

@ganeshie8

anonymous · Answer

I believe it is$$\sum_{n=0}^{\infty} $$ with (-4 + 9n) to the side...maybe

ganeshie8 · Answer

It is an arithmetic progression with 
first term = -4
common difference = 9

can you write the general term ?

ganeshie8 · Answer

Yes, -4 + 9n is the general term !

ganeshie8 · Answer

How many terms are there in total ?

ganeshie8 · Answer

-4 + 9n = 131

9n = 135

n = 15

so "n" ranges from 0 to 15, right ?

anonymous · Answer

i'm not sure how you figure that out? the sequence goes from -4 to 131 i think but can't it keep going to infinity?

ganeshie8 · Answer

-4 + 5 + 14 + 23 + ... + 131 


Notice that the sum ends with the term 131
Its not going to infinity.

anonymous · Answer

oh ok that makes sense

ganeshie8 · Answer

-4 + 5 + 14 + 23 + ... + 131   =   $\sum\limits_{n=0}^{15}(-4+9n)$

ganeshie8 · Answer

see if that looks good

anonymous · Answer

if it was going to infinity it would have '...' at the end of the sequence?

ganeshie8 · Answer

Exactly !

anonymous · Answer

ok thank you for all of your help! :)