Please help? summation notation

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1 Answer
jonathan n.
May 2, 2018

Look below

Explanation:

choice A states #sum_(k=1)^5 (-3)^k = -3 +9 - 27 +81 - 243#

Choice B states #sum_(k=1)^5 (-3)^(k+1)# which is an obvious nope

Choice C states #sum_(k=1)^5 (-1)^k 3^(k+1) = (-1*9)=-9# which is a nope, which leaves us off with choice D

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