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An infinite geometric series has common ratio $-1/5$ and sum $16.$ What is the first term of the series?

 Mar 4, 2021
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Sum = a1 / (1-r)

16 = a1 / (1- -1/5)

 

16 * 6/5 = a1 = 96/5    =   19.2

 Mar 4, 2021
edited by ElectricPavlov  Mar 4, 2021

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