Question

How many terms are there in a geometric series if the first term is 7, the common ratio is 2, and the sum of the series is 105?

Answer 1

105  =  7. (1 - 2^n) / 1-2

105*-1 = 7 (1 - 2^n)

1 - 2^n = -105/7 = - 15

2^n = 16 

n = 4 answer