Question

an=1/2an-1, where a1=20. What are the first five terms of this sequence?

Answer 1

This is also known as a recursive sequence.
Can you tell me if this is the sequence: \[a_n = \frac{1}{2a_{n-1}}\]
Or is it \[a_n = \frac{1}{2} 2a_{n-1}\] ?

Answer 2

ok lol, that clarifies things.

Answer 3

Oh lol. Got it. :)

All you have to o is find the five terms by using the first term.

You are given that a_1 = 20

\[a_2 = 1/2 * a_1 => half~~ of~~ 20 = 10\]

Continue like that, till a_5.

Getting this? :)

Answer 4

so what you'll want to do first is set n=2 and we get:
a_2 = 1/2 * a_1
and we know what a_1 is. that's 20
so substitute:
a_2 = 1/2* 20
= 10
we repeat the process for n=3, n=4, n=5

Answer 5

Okay plug n = 2 so a2 = -----------?

Answer 6

Yes. I understand now. Thanks all.

Answer 7

u r welcome :)