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2-85.

Below are two more situations that can be described using exponential functions. They represent a small sampling of the situations where quantities grow or decay by a constant percentage over equal periods of time. For each situation: Homework Help ✎

• Find an appropriate unit of time (such as days, weeks, years).

• Find the multiplier that should be used.

• Identify the initial value.

• Write an exponential equation in the form $f(x)=ab^x$ that represents the growth or decay.

1. The value of a car with an initial purchase price of $12,250 depreciates by 11% per year. If the value of the car decreases by 11% every year, then the car is worth 89% of the cost of it during the previous year. Years; 0.89; 12,250 $f(x)=12250(0.89)^{x}$ 2. An investment of$1000 earns 6% annual interest, compounded monthly.

Use a similar process as in part (a) above.