Question

Write the explicit formula that represents the geometric sequence -2, 8, -32, 128

Answer 1

Can you find the common ratio, which is defined as the ratio
\(\Large r=\frac{a_{n+1}}{a_n}\)

Answer 2

I don't think so. How would I do so?

Answer 3

-4?

Answer 4

divide 2nd term by first, 3rd term by 2nd etc to find common ratio

Answer 5

Both equal -4

Answer 6

that is what @mathmate formula states

Answer 7

oh okay. I couldn't understand.

Answer 8

now you do!, so now you have the common ratio: @mathmate will show you, next step

Answer 9

OKie Dokie.

Answer 10

Theoretically he will... lol

Answer 11

Well there is one person who know @acxbox22

Answer 12

@BPDlkeme234 wow you are being nice good job i knew you could do it

Answer 13

Thank you for simplifying thing for me @BPDlkeme234 !

Answer 14

*things

Answer 15

Just relying on your expertise here! @acxbox22

Answer 16

http://www.regentsprep.org/regents/math/algtrig/atp2/geoseq.htm
to find the common ration divide the second term by the first
8/-2=-4 like stated above

Answer 17

its a simple geometric sequence!

Answer 18

r=-4 (r is the common ratio)

Answer 19

yes, we covered that

Answer 20

never hurts to restate it anyway to make it clear @BPDlkeme234

Answer 21

true!

Answer 22

So is that the answer then? @acxbox22 @BPDlkeme234

Answer 23

yes

Answer 24

wait for it @Jonnychewy

Answer 25

no we are not at the formula yet, @acxbox22 is coming up with it..give him some time!

Answer 26

in the meantime the formula for a geometric sequence is Tn = ar ^n-1

Answer 27

xn=ar^(n-1) is the formula
where a is the first term and r is the ratio

Answer 28

we have those values so we can sub them into the formula to get the answer

Answer 29

@acxbox22 has already calculated r you see!