8-2: Exponential Decay Day 2 Objective Ca Standard 12: Students know the laws of fractional exponents, understand exponential functions and use these functions in problems involving exponential growth and decay.

Exponential Decay Models When a real life quantity decreases by a fixed percent each year (or other time period), the amount of the quantity after t years can be modeled by the equation where a is the initial amount, and r is the percent decreased expressed as a decimal. The quantity 1 - r is the decay factor

Example 2: You buy a new car for $30,000. The value y of the car decreases by 16% per year. Write an exponential decay model for the value of the car. Use the model to estimate the value of the car after 2 years.

When t = 2 the value is

Graph the Model Plot these points: (0, 30,000), (1, 25,200), (2, 21,118). Use the graph to estimate when the car will have a value of $10,000

-About 6 years

8 – 2 day 2 Home Work page – 45, 49 – 51, 56 – 64 even