Question

Which expression could be used to find the sum of the first n terms of the geometric sequence that begins 11,22,44,…?


#1
n2(11+2(n−1))

#2
n2(22+2(n−1))

#3
22n−1

#4
11(2n−1)

Answer 1

= 11( - 1)
Step-by-step explanation:
The sum to n terms of a geometric sequence is
=
where a₁ is the first term and r the common ratio
Here a₁ = 11 and r = = = 2 , then
= = 11 ( - 1)