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What is the sum of the first 5 terms?

2. Find the sum of the first 5 terms of the geometric series:
1/18 - 1/6 + 1/2 - ...

 

i think its 35/18

 Apr 19, 2019
 #1
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The common ratio  is   -3   

 

So....the sum of the 1st 5 terms  is

 

(1/18) [ 1 - (-3)^5 ] / [ 1 -  (- 3 ) ]  =

 

(1/18) [ 244 ] / 4  =

 

244 / 72  =

 

61 / 18

 

cool cool cool

 Apr 19, 2019

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