Question

Which choice is the explicit formula for the following geometric sequence?

0.5, -0.1, 0.02, -0.004, 0.0008, ...

A. an = 0.5(0.2)^n
B. an = 0.5(-0.2)^n-1
C. an = -0.5(0.3)^n-1
D. an = -0.5(0.2)^n-1
E. an = -0.5(-0.2)^n-1

Answer 1

@Godlovesme could you help?

Answer 2

im lost on how to find the answer on this..

Answer 3

me too lol

Answer 4

lol do you know anyone who could help us?
cause this stuff is blah. xD

Answer 5

fr!!! C:
@sammixboo @Loser66 help?

Answer 6

well the method to get to the answer. not neccisarly give it to me. but help me get to it and guide me on what i do wrong

Answer 7

0.5 is the \(1^{st}\) number, right? that is n =1

Answer 8

so, \(a_1 = 0.5\)

Answer 9

yes

Answer 10

now, I test the first option: \(a_1= 0.5 * (0.2)^1 =??\) pretty sure that for the first option, \(a_1\) can't be 0.5, right?

Answer 11

Ok yea?

Answer 12

Now, I test the second option: \(a_1 = 0.5*(-0.2)^{1-1}=0.5*(-0.2)^0=0.5\) oh yeah... sounds good

Answer 13

No need to test the rest, since for n =1, their \(a_1) = - 0.5, so, they are not the correct answer.

Answer 14

sorry my internet went to poop..

Answer 15

so the 0.5 and 0.2 will both be negative?
I am a little confused...

Answer 16

All you need is doing the same for the second term \(a_2\) with the second option to make sure that you are correct when choosing it.

Answer 17

the given second term is -0.1
now , test the formula of b) it says \(a_2 = 0.5*(-0.2)^{2-1}=0.5*(-0.2)^1=0.5*(-0.2)=-0.1\) bingo