How we can evaluate this : ∑2ⁿ from k=1 to n , as n→-∞ ?

1 Answer
Apr 13, 2018

sum""_(k=1)^(n->-oo) =4

Explanation:

The series is just
2 + 1 + 1/2 + 1/4 + ...
That is a geometric series with
a=2, r=1/2
So the sum is a/(1-r) = 2/(1-1/2)