Question

What is the sum of the geometric series?

Answer 1

$\Sigma_{n=1}^{4}-2\cdot(-3)^{n-1} \\(-2)(-3)^{1-1}+(-2)(-3)^{2-1}+(-2)(-3)^{3-1}+(-2)(-3)^{4-1} \\-2+6-18+54 \\\boxed{40}$

So the answer is C,

$\Sigma_{n=1}^{4}-2\cdot(-3)^{n-1}=40$

Hope this helps.

r3t40