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_____________

 Mar 21, 2019
 #1
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This is a geometric series

The first term =  5

The common ratio is -2

 

The sum of the first five terms is

 

first term [  1 - common difference^5] / [ 1 - common difference ]

 

5  [ 1 - (-2)^5 ] / [ 1 - (-2) ]  =

 

5 [ 1 + 32 ]  / [ 3]  =

 

5 { 11]  = 

 

55

 

 

cool cool cool

 Mar 21, 2019

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