Question

What is the sum of the geometric sequence 1, 3, 9, ... if there are 11 terms?

29,524
55,987
87,381
88,573

Answer 1

\( \color{Black}{\Rightarrow S = a \times\Large{1 - r^n \over 1 -r} }\)

substitute r with 3(we're multiplying 3 everytime), n with 11.

Answer 2

a is the first term aka 1.