+0  
 
0
141
1
avatar+412 

Find the sum of the first seven terms: 1/2 + 1 + 2 +4 +...

 

7.5

 

63.5

 

55.5

 

31.5

 Apr 29, 2019
 #1
avatar+106515 
+1

The common ratio is 2....so....

 

Sum   =   first term  [ 1 - common ratio^7 ]   / [ 1 - common ratio ]  =

 

(1/2) [ 1 - 2^7 ] / [ 1 - 2 ]    =

 

(1/2) [ -127] / [ -1]  =

 

(1/2) (127)  =

 

63.5

 

cool cool cool

 Apr 29, 2019

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