If the first n terms of the equal ratio sequence {an} and Sn = k · 2 ^ n + 1, then the value of K is____ a) 1 b) - 1 c) 2 D) K can be any value

If the first n terms of the equal ratio sequence {an} and Sn = k · 2 ^ n + 1, then the value of K is____ a) 1 b) - 1 c) 2 D) K can be any value

This problem is to investigate the understanding of the formula of equal ratio sequence. The general equal ratio sequence has Sn = A1 (1-Q ^ n) / (1-Q). After simplification, it is found that the coefficient of constant term is A1 / (1-Q), and the latter is his opposite number. The coefficient of constant term given by that formula is 1. Obviously, K should be - 1. The answer is B