Question

HELP ME
Which of the following choices is the explicit formula for the following geometric sequence?

-0.1, 0.04, -0.016, 0.0064, -0.00256, ...

A.an = 0.1(-0.4)n-1
B.an = -0.1(0.4)n-1
C.an = 0.1(0.4)n
D.an = 0.4(-0.4)n-1
E. an = -0.1(-0.4)n-1

Answer 1

first find the common ratio
0.04/-0.1=?

Answer 2

the explicit formula for a geometric sequence is
\(\Large a_n=ar^{n-1}\)
a is the first term and r is the common ratio

Answer 3

ok wait

Answer 4

a=-0.1

Answer 5

r=?

Answer 6

0.4?

Answer 7

no

Answer 8

i mean 1

Answer 9

-0.4

Answer 10

ok but that next number is gonna be a positive

Answer 11

yeah and it is positive
there is an oscillation of sign because of that negative

Answer 12

o ok i got you

Answer 13

-0.1x-0.4=0.04
0.04x-0.4=-0.0016....

Answer 14

you continue like that to generate as many term as you like

Answer 15

so its a

Answer 16

so r=-0.4

Answer 17

no A is incorrect

Answer 18

first term is -0.1 not 0.1

Answer 19

ok wait

Answer 20

so e

Answer 21

yes!

Answer 22

thx ima tag you my next question later on

Answer 23

np:)