Question

Given an arithmetic sequence in the table below, create the explicit formula and list any restrictions to the domain.

Answer 1

n a_n
1 9
2 3
3 -3

Answer 2

A. a_n = 9 − 3(n − 1) where n ≤ 9
B. a_n = 9 − 3(n − 1) where n ≥ 1
C. a_n = 9 − 6(n − 1) where n ≤ 9
D. a_n = 9 − 6(n − 1) where n ≥ 1

Answer 3

so, you know the formula is
an = a1 +(n-1)d

a1 = 1st term = 9
can you find the common difference d = ... ?

Answer 4

or know what common difference means ?

Answer 5

Can you walk me through it? I think the common difference is 3..??

Answer 6

ok, sure
common difference means the difference from next term to current term!
so, d = 2nd term - 1st term = 3rd tem - 2nd term = 4th term -3rd term

got this ?

Answer 7

Kinda...

Answer 8

here,
d = 3-9 = -3 - (3) = ...?

Answer 9

let me give you something to read,
maybe you'll understand more....
Tutorial on AP,GP,HP.
http://openstudy.com/study#/updates/503bb2a0e4b007f900310

Answer 10

so what you got d here ?

Answer 11

-6?

Answer 12

d = -6 is correct :)

Answer 13

an= a1 +(n-1)d = 9 + (n-1)(-6)

Answer 14

so which choice ?
also not that 'n' is natural number, because we count it, 1st term, 2nd term and so on...so it has to be n >=1

Answer 15

a_n=9-6(n-1) where n ≥ 1

Answer 16

correct! :)

Answer 17

You're the best! :D

Answer 18

thank you for the compliment :)
always happy to help :)