$\"\"$

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The given sequence $\"\"$ .

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Where $\"\"$

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The nth term of a geometric sequence formula $\"\"$ .

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Where $\"\"$ is first term and r is common ratio.

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$\"\"$ (Substitute $\"\"$ )

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$\"\"$ (Subtract power: $\"\"$ ) $\"\"$

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Apply division property of equality: a = b then $\"\"$ .

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$\"\"$ (Divide each side by 9)

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$\"\"$ (Cancel common term)

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$\"\"$ (Divide: $\"\"$ )

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$\"\"$ (Evaluate powers: $\"\"$ )

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$\"\"$ (Apply fourth root of each side and eliminate power) $\"\"$

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When $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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The geometric means are 18, 36, 72. $\"\"$

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When $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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The geometric means are $\"\"$ . $\"\"$

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The geometric means are 18, 36, 72 or $\"\"$ .