OpenStudy (anonymous):

Find the indicated sum for the arithmetic series. S16 for 12 + 7 + 2 + (-3) + ...

OpenStudy (cwrw238):

what is the common difference for this series?

OpenStudy (anonymous):

5

OpenStudy (cwrw238):

not quite - notice that the numbers decrease

OpenStudy (anonymous):

-5?

OpenStudy (cwrw238):

yes and Sn = (n/2)[2a1 + (n-1)d] where n = no. of terms, a1 = first term and d = common difference

OpenStudy (cwrw238):

so pug in your values and work it out

OpenStudy (cwrw238):

* plug

OpenStudy (anonymous):

Thank yoou (: