# The resale value of a textbook decreases by 25% with each previous owner. A new textbook is sold for $85. What is the function represents the resale value of the textbook after x owners?

##### 2 Answers

It is not linear. It is an exponential function.

#### Explanation:

If a new book worths $85, then used once book worths $63.75.

Used twice book worths $47.81

Used three times book worths $35.86

etc.

Now your equation (I computed this using Microsoft Excel)

x represents owner number. For example 5th owner of the book buys this book

etc.

Where

#### Explanation:

Let new cost after each sale be

The first reduction is:

This is the same as:

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Set as

But

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This process repeats for each successive depreciation.

So for

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