$\"\"$ \ \

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(a)

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Melina receives a chain e-mail, forwards it to $\"\"$ friends, and each friend forwards it to $\"\"$ friends.

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Thus, $\"\"$ , $\"\"$ and $\"\"$ .

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Find the common ratio $\"\"$ .

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$\"\"$

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$\"\"$ .

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For an explicit formula, substitute $\"\"$ and $\"\"$ in the $\"\"$ term formula.

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$\"\"$ .

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$\"\"$ .

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$\"\"$

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(b) Find $\"\"$ .

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$\"\"$ .

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$\"\"$ .

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Therefore, after $\"\"$ forwards $\"\"$ people will have received the e-mail.

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$\"\"$

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(a) Explicit formula: $\"\"$ .

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(b) After $\"\"$ forwards $\"\"$ people will have received the e-mail. \ \