Question

What is the 20th term of the sequence that begins -3,6,-12,24...?
A.-524288
B.524,288
C.1,572,864
D. 3,145,728

Answer 1

can you see a pattern here
Hint: each term is obtained from the previous by multiplying by a sertain number - can you see which number?

Answer 2

3?

Answer 3

no

6 / -3 = ?

Answer 4

-2??

Answer 5

-12/6 = ?

Answer 6

yes -2

Answer 7

ah gotchaa! okk

Answer 8

this is a geometric sequence
and the formula for the nth term is a1*r^(n-1)
where a1 = first term and r = common ratio

Answer 9

in this case a1 = -3 and r = -2

so 20th term = -3 * (-2)^(20-1)
= -3 * (-2)^19

Answer 10

can you work that out - use calculator of course

Answer 11

i got 1572864?? :S i feel like thts wrong

Answer 12

no thats correct

Answer 13

ahhh it is indeed ^.^ sorry. thank you!!

Answer 14

yw