Finding the sum of sigma notations?

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I understand how to do the rest of the problem but I'm not sure how to get the eight? Can someone please list step by step how to get the sub 8 and thanks in advance!

1 Answer
Jim G.
Dec 6, 2017

#"see explanation"#

Explanation:

#"your calculation is correct"#

#"summing the terms of a geometric sequence with"#
#"a=5 and r "=1/7#

#"note that "sum_(n=0)^7a_n" is the sum of 8 terms"#

#a_0+a_1+a_2+a_3+a_4+a_5+a_6+a_7larrcolor(blue)"8 terms"#

#rArrS_8=(5(1-(1/7)^8))/(1-1/7)=5.833#

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