Question

For the following G.P.'s, find S_n: 3, 6, 12, 24, ...

Answer 1

3, 6, 12, 24, ...

Here, a = 3, r = `6/3` = 2 > 1

S_n = `("a"("r"^"n" - 1))/("r" - 1)`, for r > 1

∴ S_n = `(3(2^"n" - 1))/(2 - 1)`

∴ S_n = 3(2ⁿ – 1)