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Section 6.2 Exponential Function Modeling and Graphs. The number of asthma sufferers in the world was about 84 million in 1990 and 130 million in 2001. Let N represent the number of asthma sufferers (in millions) worldwide t years after 1990.
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The number of asthma sufferers in the world was about 84 million in 1990 and 130 million in 2001. Let N represent the number of asthma sufferers (in millions) worldwide t years after 1990. • Write N as a linear function of t. What is the slope? What does it tell you about asthma sufferers? • Write N as an exponential function of t. What is the growth factor? What does it tell you about asthma sufferers? • Graph the two together. What do you notice?
The half-life of a substance is the amount of time it takes for a decreasing exponential function to decay to half of its initial value • The half-life of iodine-123 is about 13 hours. You begin with 100 grams of iodine-123. • Write an equation that gives the amount of iodine remaining after t hours • Hint: You need to find your rate using the half-life information • How much iodine-123 will be left after 1 day?
Doubling time is the amount of time it takes for an increasing exponential function to grow to twice its previous level • Suppose we put $1000 in the stock market 10 years ago and we now have $2000 • Write an equation for the balance B after t years • What was the annual growth rate?
Consider the following table • How can we determine if this data can be represented by an exponential function? • Test for a constant ratio • Find a function for this situation • For what value of t does h(t) = 2000?
In your groups graph the following exponential functions on the same screen • Use a window with -5 ≤ x ≤ 5 and 0 ≤ y ≤ 70 • What do you notice about the graphs • What are there y-intercepts? • Are they decreasing or increasing? • Are they concave up or concave down? • What are their domains and ranges?
Let’s look at the following graphs • What is going on with these graphs? • What can you say about their y-intercepts? • What can you say about the rate they are increasing?
Horizontal Asymptotes • All exponential functions have a horizontal asymptote • This is the place where the function “levels off” • It is at the horizontal axis (unless the exponential function has been shifted up or down) y x
Let’s try a few from the chapter 6.2 – 6, 7, 14, 15, 21, 22, 33