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Homework Questions!
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Exploring Exponential Models
Unit 3 Exploring Exponential Models
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An exponential function is a function with the general form of:
y = abx where x is a real number, a ≠ 0, b > 0, and b ≠ 1.
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Graphing Exponential Equations
y = 2x x y -3 -2 -1 1 2 3
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EXPONENTIAL GROWTH y = a • bx time initial amount growth factor (1+r)
Ex. The population of the US in 1994 was about 260 million with an average annual rate of increase of about 0.7%. 1. Write a function to model this population. 2. What was the population in 2006?
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Modeling growth The bear population increases at a rate
of 2% per year. There are 1573 bears this year. Write a function that models the bear population. How many bears will there be in 10 years?
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Exponential Decay y = a(1-r)t Ex. 1. Suppose you want to buy a used car that costs $11,800. The expected depreciation of the car is 20% per year. Estimate the depreciated value of the car after 6 years.
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More Decay….. Ex. 2. The population of a certain animal species decreases at a rate of 3.5% per year. You have counted 80 animals in the habitat. Write the equation.
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Ex: Analyzing a Function
Without graphing, determine whether the function y = 14(0.95)x represents exponential growth or exponential decay. Without graphing, determine whether the function y = 0.2(5)x represents exponential growth or exponential decay.
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An asymptote is a line that a graph approaches as x or y increases in absolute value.
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Ex: Graphing Exponential Decay
y = 24(1/3)x Identify. Horizontal Asymptote Domain Range x y -3 -2 -1 1 2 3
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Example 5b Graphing Exponential Decay
y = 100(0.1)x Identify. Horizontal asymptote Domain Range x y -3 -2 -1 1 2 3
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Example 2 Translating y = abx
y =8(1/2)x y = 8(1/2)x+2 +3
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Example 2b Translating y = abx
y =2(3)x-1 + 1 y = -3(4)x+1 +2
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Half-life! A = A0(1/2) What does that mean?
The half-life is the amount of time it takes for half of the atoms in a sample to decay. * t A = A0(1/2) Half life
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Example 3 Real World Connection
A hospital prepares a 100-mg supply of technetium-99mg which has a half-life of 6 hours. Write an exponential function to find the amount of technetium-99mg that remains after 75 hours.
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Another Half-Life? Arsenic-74 is used to locate brain tumors. It has a half-life of 17.5 days. Write an exponential decay function for a 90-mg sample. Use the function to find the amount remaining after 6 days.
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Classwork/homework Worksheet
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