Question

Which summation formula represents the series below? 12 – 24 + 48 – 96

Answer 1

The summation formula for the series given by:
 12 – 24 + 48 – 96
will be calculated as follows:
first term,a=12
common ratio=+/-2
thus the sum will be:
(i=1)Σ[12(-2)^(i-1)]

Thus the answer:
(i=1)Σ[12(-2)^(i-1)]