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The first term of a geometric sequence is 8, and the second term is 4. Find the fifth term. ?

1 Answer

Jul 19, 2018

$a_{5} = \frac{1}{2}$ $a_5=1/2$

Explanation:

The common ratio $r$ $r$ is:
$r = \frac{4}{8} = \frac{1}{2}$ $r=4/8=1/2$

Write a formula:
$a_{n} = 8 {(\frac{1}{2})}^{n - 1}$ $a_n=8(1/2)^(n-1)$

So the fifth term would be:
$a_{5} = 8 {(\frac{1}{2})}^{5 - 1}$ $a_5= 8(1/2)^(5-1)$

$a_{5} = \frac{8}{16} = \frac{1}{2}$ $a_5=8/16=1/2$

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