contestada

what is the sum of the geometric sequence -4,24, -144, ... if there are 6 terms?

A. -159,963
B. 26,660
C. 26,661
D. 159,963

Respuesta :

apologiabiology
each term is multiplied by -6 to get next term
first term is -4

a1=-4
r=-6

the sum is
[tex]S_n=\frac{a_1(1-r^n)}{1-r}[/tex]
a1=-4
r=-6
n=6 because we want 6 terms

[tex]S_6=\frac{-4(1-(-6)^6)}{1-(-6)}[/tex]
[tex]S_6=\frac{-4(1-46656)}{1+6}[/tex]
[tex]S_6=\frac{-4(-46655)}{7}[/tex]
[tex]S_6=\frac{186620}{7}[/tex]
[tex]S_6=26660[/tex]

answer is B

Answer:

26,660

Step-by-step explanation: