+0  
 
0
156
2
avatar+4690 

Help 16

 Mar 19, 2018
 #1
avatar
0

∑[ 2*0.25^x, x, 0, 15] =2 2/3 =~3

 Mar 19, 2018
 #2
avatar+96368 
+1

Sum of  the first n terms of a geometric series  =

 

First term   [  1  -  common ratio^n]  /  [ 1  -  r]

 

Here.....r  =  (1/4)  and n  =  15

 

So we have

 

2  [  1 - (1/2)^15] / [ 1 - 1/2]  =

2[ 1 - (1/2)^15] / (1/2)=

4 [ 1 - (1/2) ^15]  =  3.999 ≈ 

4

 

cool cool cool

 Mar 20, 2018

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