Question

Find an explicit rule for the nth term of a geometric sequence where the second and fifth terms are -36 and 2304, respectively.

Answer 1

@welshfella this is my last question

Answer 2

Find an explicit rule for the nth term of a geometric sequence where the second and fifth terms are -36 and 2304, respectively.

an = 9 • 4^n
an = 9 • (-4)^(n + 1)
an = 9 • 4^(n - 1)
an = 9 • (-4)^(n - 1)

Answer 3

From an example, I think you do something like \[2304=-36*r^3 \]
or something like that

Answer 4

second term is a1r and 5th term is ar^4
so r^4 / r = r^3 = 2304 / -36

Answer 5

so r^3 = -64

so what is the value of r ?

Answer 6

cube root of -64?

Answer 7

-4

Answer 8

So that's the first term?

Answer 9

no that;s the common ratio r

Answer 10

so thats excludes the first and third option where r = 4

Answer 11

okay so we need to figure if it's n+ 1 or n-1

Answer 12

when u finish welsh

Answer 13

first term = a1 and second term = a1 * -4 = -36
so a1= -36 / -4 = ?

Answer 14

9

Answer 15

do u follow that?

Answer 16

yes its 9
and the exponent is always n-1

Answer 17

yes i do

Answer 18

is there anytime when it would be n+1?

Answer 19

no

Answer 20

welsh i respond the question u ask me on my post come take a look

Answer 21

Okay thanks for all the help again! :)

Answer 22

yw

the general formula for the nth term an = a1. r^(n-1)

- always n-1