Question

Find the sum of the first twelve terms of the sequences 3, -6, 12, -24,..
Show your work.

Answer 1

3, -6, 12, -24, 48, -96, 192, -384, 768, -1536, 3072, -6144...

×-2

Geometric sequence

Answer 2

if we look at the pattern, we have

let x = 3

x, -2x, 4x, -8x etc


which means what we need is

x + 4x + 16x + 64x, 256x, 1024x - 2x - 8x - 32x - 128x - 512x - 2048x

This is equal to -4113.