Question

Evaluate using the sum of a finite geometric series:
The sum of 2^i on the range from i = 1 to n. Please Help! I don't know how to make the exponent in 2^i = to i-1!

Answer 1

2^1 +2^1 *2^1 + 2^1* 2^2 ..... 2^1*2^(n-1)
is
2 + 2*2 + 2 *2^2 ....
note 2^1 * 2^(n-1) = 2^n

2^1 =2 = a
2 = r

sum from i = 1 to n
= 2 ( 1-2^n)/(1-2) = -2 (1-2^n) =2^(n+1) - 2