Exponential Functions and Exponential Functions and Their GraphsTheir Graphs
Exponential Functions and Exponential Functions and Their GraphsTheir Graphs
Rules for Exponents• Exponents give us shortcuts for
multiplying and dividing quickly.
• Each of the key rules for exponents has an important parallel in the world of logarithms which is learned later.
Properties of Exponents
Product Rule:
86
2
aa b
bx xx x
xx Quotient
Rule:
Power Rule 23 6ba abx x x x
4 2 6a b a bx x x x x x
Multiplying with Exponents
• To multiply powers of the same base, keep the base and add the exponents.
x y x x x y
x y x y
7 3 5 7 5 3
7 5 3 12 3
Keep x, add exponents 7 +
5
Can’t do anything about the y3 because
it’s not the same base.
Dividing with Exponents
7 5
7 5
7
7
5
5
7 5 7 5
10 12
6 4
10
6
12
4
10 6 12 4 4 8
• To divide powers of the same base, keep the base and subtract the exponents.
Keep 7, subtract 10-
6
Keep 5, subtract 12-
4
Powers with Exponents• To raise a power to a power,
keep the base and multiply the exponents.
This means t7·t7·t7 = t7+7+7
213737 )( ttt x
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The exponential function f with base b is defined by f (x) = abx where a 0, b 0 or 1, and x is any real #.
a is the initial value and b is the base; x is the power to which the base is raised.These are examples of exponential functions:
12 2
12(.25)
t
x
g t
f x
a ,the # outside the ( ) is the y-intercept or
the initial value of the function.
Exponential functions are often asymptotic to the x-axis, meaning
they get closer and closer and closer to it, but can never reach it because
y cannot equal zero.
y =abx
If b > 1, the exponential is increasing, growing as the values of x go up from left to right.
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Graph of f(x) = abx, b > 1y
x(a, 1)
Domain: (–, )
Range: (0, )
Horizontal Asymptote y =
0
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Graph of f (x) = abx, 0<b <1
y
x
(0, 1)
Domain: (–, )
Range: (0, )
Horizontal Asymptote y = 0
If 0 < b <1, the function is a decreasing exponential.
Determine if the graphs below represent increasing or decreasing functions.
Y=4(1.5)x f(x)=10(1.2)x
Y=6(.42)x F(x)=12(.88)x
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What do you notice about the functions:
( ) xf x a( ) xf x a and
They are reflections across the y-axis.
Identify the initial value and the rate of change for each exponential function below. Are they increasing or decreasing?
1. ( ) 12(0.45)
2. ( ) 50(1.23)
33. ( ) 20
5
x
x
x
f x
g x
h x
Transformations of Exponential Functions
Compare the following graph of f(x)=3x and y= 3x+1
Compare the following graph of f(x)=3x and y = 3x-2
f(x)=3x
y = 3x-2
What happened in each case?
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Sketch the graph of g(x) = 2x – 1. State the domain and range.
Domain: (–, ) Range: (–1, )
Y=-1 is the horizontal asymptote
b is the rate of change in the function.b = 1 ± r
where r = the % of change
Nowheresville has a population of 3138. If the population is decreasing at a yearly rate of 3.5%, write an equation to represent this function and determine the population in 5 years.
Y=abx
Mrs. Layton has $5000 to invest in a starting company. If they promise a 6% rate of return each year, what formula
represents this exponential function? In 5 years, how much will her investment be
worth?
Y=abx
Sometimes, rather than an integer, the base of the exponential
function is the irrational number, e.
e is approximately equal to 2.781828… but, because it is irrational, its integers do not repeat in a recognizable pattern.
3 xy e would be an increasing exponential since its base, e, is greater than 1.
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Graph of f(x) = ex
y
x2 –2
2
4
6
X-axis is the horizontal asymptote
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