27263pcp1gl 27263pcp1gl
  • 30-07-2018
  • Mathematics
contestada

What is the sum of the geometric sequence -4, 24, -144, ... if there are 7 terms?

A: -159,964
B: -26,661
C: 26,661
D: 159,963

Respuesta :

gmany
gmany gmany
  • 30-07-2018

[tex]a_1=-4;\ a_2=24;\ a_3=-144;\ ...\\\\r=\dfrac{a_2}{a_1}\\\\r=\dfrac{24}{-4}=-6[/tex]

The formula of the sum of a geometric sequence:

[tex]S_n=\dfrac{a_1(1-r^n)}{1-r}[/tex]

We have:

[tex]a_1=-4;\ r=-6;\ n=7[/tex]

substitute:

[tex] S_7=\dfrac{-4(1-(-6)^7)}{1-(-6)}=\dfrac{-4(1-(-279,936))}{1+6}=\dfrac{-4(1+279,936)}{7}\\\\=\dfrac{-4\cdot279,937}{7}=-159,964 [/tex]

Answer: A: -159,964

Answer Link

Otras preguntas

(0,-3);m=-2 what is the parallel
Of the cans of peaches inspected yesterday at a certain plant, 1.5 percent failed to pass inspection. of the cans that failed inspection, 5/6 were incorrectly l
A 1 lb. package has 10 hot dogs. How much of an ounce does each hot dog weigh.
Where do you find an elements energy levels
what is the preposition of this sentence: the incas kept records of their possessions with special knotted cords called quipu.
The President of America famously pardons a turkey every year. Can you locate in the find a word the turkey pardoned by Barack Obama?
Two friends share 7 cookies equally.how many cookies does each friend get.
Kanesha meets with a therapist because she wants to do something about the path her life is taking. the doctor tells her to lie down on the couch, relax, and sa
help please............
Is the following sentence punctuated correctly? Elizabeth said she was unhappy. A: correct B: incorrect