Question

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

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

Answer 1

what it is the common difference
that is what are the following:
5-(-4)=?
14-5=?
23-14=?

Answer 2

9 @freckles

Answer 3

right
and we know a arithmetic sequence is of the form:
\[a_n=a_1+d(n-1) \\ \text{ where } a_1 \text{ is first term } \\ \text{ and } d \text{ is common difference } \\ \text{ your answer will be of the form } \sum_{i=1}^{n} a_i=\sum_{i=1}^n [a_1+d(i-1)]\]
so the only thing left to figure out is the n for which you get the last term 131

Answer 4

for what n is a_n =131
well just solve:
\[131=a_1+d(n-1)\]
where you found d to be 9

Answer 5

wait so what do i do next? @freckles

Answer 6

did you find n yet?

Answer 7

for when an is 131

Answer 8

because that is basically the last step besides to plug into the final form

Answer 9

No I didn't find it

Answer 10

ok well do you still need any help?

Answer 11

I'm not sure if that means you are having a problem solving the equation I gave you or not