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sum to n terms of the series 1/2+3/4+7/8+15/16.... is? solve it for me please

 

[answer: (2^-n)+n-1]

 Jul 14, 2016

Best Answer 

 #1
avatar+33653 
+15

Write the series as:  

(1-1/2) + (1-1/4) + (1-1/8) + ... + (1-1/2^n)  →  n - (1/2 + 1/4 + 1/8 + ... + 1/2^n)

 

The term in brackets is a geometric series whose sum is given by (1/2)*(1-1/2^n)/(1-1/2) → 1-1/2^n

 

So. (1-1/2) + (1-1/4) + (1-1/8) + ... + (1-1/2^n)  → n - (1  - 1/2^n) or 2^(-n) + n - 1

.

 Jul 14, 2016
 #1
avatar+33653 
+15
Best Answer

Write the series as:  

(1-1/2) + (1-1/4) + (1-1/8) + ... + (1-1/2^n)  →  n - (1/2 + 1/4 + 1/8 + ... + 1/2^n)

 

The term in brackets is a geometric series whose sum is given by (1/2)*(1-1/2^n)/(1-1/2) → 1-1/2^n

 

So. (1-1/2) + (1-1/4) + (1-1/8) + ... + (1-1/2^n)  → n - (1  - 1/2^n) or 2^(-n) + n - 1

.

Alan Jul 14, 2016
 #2
avatar+129842 
0

Very nice, Alan !!!!!

 

 

 

 

cool cool cool

 Jul 14, 2016

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