Find the exact value of the 8th term of the geometric sequence: 648,216,72,24

a).30

b) 8

___

2481

c) 8

___

9

d) 8

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27

The sequence multiplies by 1/3.

Using the formula for a geometric sequence:

a (n) = a (1) * r^ (n-1)

So ...

a (n) = 648 * (1/3) ^ (n-1)

Plugging in 8 for n produces:

a (n) = 648 * (1/3) ^ (7)

Using a calculator, I find the answer to be 0.296296296 ...