Question

What is the sum of the geometric series?

4
E (-2)(-3)^n-1
n=1

A. –122
B. –2
C. 40
D. 54

Answer 1

`</p><p>\Sigma_(n=1)^(4)-2\cdot(-3)^(n-1) \\</p><p>(-2)(-3)^(1-1)+(-2)(-3)^(2-1)+(-2)(-3)^(3-1)+(-2)(-3)^(4-1) \\</p><p>-2+6-18+54 \\</p><p>\boxed{40}</p><p>`

So the answer is C,

`\Sigma_(n=1)^(4)-2\cdot(-3)^(n-1)=40`

Hope this helps.

r3t40