Question

What is the sum of a 12-term arithmetic sequence where the last term is 13 and the common difference is -10?

Answer 1

Please tell me how to do it so that I can learn.

Answer 2

I sthat the equation I should use

Answer 3

Forget equations...
The terms going backwards are
13 3 -7 -17 -27 -37 -47 -57 -67 -77
Fast enough to do on your calculater
There...i already have the answer

Answer 4

ooop i forgot the last 2 terms -87 -97

Answer 5

It says sum, so that means I would have to add all of those together right.

Answer 6

correct

Answer 7

13+3-7-17-27-37-47-57-67-77-87-97

Answer 8

I got -370

Answer 9

I get -504

Answer 10

oh I see what i did wrong

Answer 11

Great Thanks for your help