Question 985810
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The first term is {{{a}}} = 8.


The common ratio is {{{q}}} = -2.


The sum of the first 9 terms is


{{{s}}} = {{{a}}}.{{{(q^n-1)/(q-1)}}} = {{{8}}}.{{{((-2)^9-1)/(-2-1)}}} = {{{8}}}.{{{(-512-1)/(-3)}}} = {{{8}}}.{{{(-513)/(-3)}}} = 8*171 = 1368.