Question

What is the sum of the geometric sequence -4,24,-144... If there are 8 terms?

Answer 1

add

Answer 2

do you know how to get from one term to the next?

Answer 3

No

Answer 4

it is geometric, which means you get from one term to the next by multiplying by some fixed number

Answer 5

to find that number, divide any term by the previous one

Answer 6

Do I multiply by -6?

Answer 7

yes

Answer 8

now there is a formula you can use involving the first term, \(-4\)
the number of terms \(8\) and the common ratio \(-6\)
but 8 is not such a big number that you cannot just add them up

Answer 9

959,780?

Answer 10

\[-4+(-4)(-6)+(-4)(-6)^2+(-4)(-6)^2+(-4)(-6)^3+(-4)(-6)^4\\
+(-4)(-6)^5+(-4)(-6)^6+(-4)(-6)^7\]

Answer 11

that is not what i got

Answer 12

oh but i made a mistake, let me try again

Answer 13

yeah that is right

Answer 14

what you got