Question

What is the sum of the geometric sequence -4 24 -144 if there are 8 terms

-959,781

29,637

26,661

959,780

Answer 1

959,780

Explanation:

The method above is correct; however, as Yoda would say "there is another"

You can also use the Geometric series formula to solve this.

This formula is
`S_(n) = (a_(1)-a_(1)r^(n) )/(1-r)`

(n being the number of terms,
`a_(1)` being the first term, and r being the rate of change)

n = 8

`a_(1)` = -4

r = -6

Plug these values into the equation and you get 959,780.

Answer 2

The correct answer is 959,780.

In order to find this, we need to first find all the first 8 terms of the series. Each term is the previous term multiplied by -6. This gives us the following terms.

-4

-4*-6 = 24

24*-6 = -144

-144*-6 = 864

864*-6 = -5,184

-5,184*-6 = 31,104

31,104*-6 = -186,624

-186,624*-6 = 1,119,744

Now we add all those together and get our answer.

-4 + 24 - 144 + 864 - 5,184 + 31,104 - 186,624 + 1,119,744 = 959,780