Question

What are the next three terms of the sequence 1, -3, 9, -27,…?

A. -54, 162, -486
B. -81, 243, -729
C. 81, -243, 729
D. 57, -162, 486

Answer 1

Ridiculous problem. Finite sequences have infinitely many "next three terms". ANYTHING you can justify is an acceptable answer.

1, -3, 9, -27, 0, -2, 5 -- That works.
1, -3, 9, -27, 28, -29, 5 -- That works.
1, -3, 9, -27, \(\sqrt{5}\), \(\pi\), e -- That works.

What say you? Give us a clue what YOU might think are three acceptable values and justify your response.

Answer 2

Well, I thought it was 57, -162, 486, but I really wasn't sure, so I came on here for some help..

Answer 3

It's not a matter of being sure. It's a matter of justifying your answer. How did you get those three values?

Answer 4

If you're having trouble with this, try breaking it down. The sequence itself has 4 values in it already. What did the 1 do to become -3?

Answer 5

Generally, it's a good idea to look for common differences or common ratios.

Subtract each successive pair. What do you get?
Divide each successive pair. What do you get?

Answer 6

i really don't understand

Answer 7

1*(-3) =?

Answer 8

-3

Answer 9

Now, second term
-3*(-3) =?

Answer 10

9

Answer 11

Now, third term
9*(-3) =?

Answer 12

-27

Answer 13

can you see your answers are the term of the given sequence??

Answer 14

oh, yeah! Thank you so much! I get it now :)

Answer 15

so, next will be???

Answer 16

81

Answer 17

then it'll be -243

Answer 18

Yes!! look at your options, which is correct.

Answer 19

c! Thanks again :)

Answer 20

No need to do next, since there is only 1 option which starts at 81, It is C

Answer 21

YOu got it. hehehe...