Accelerated Precalculus. Name: Graphing exponential and logarithmic functions.
Exponential function ... The graph of the basic exponential function ( ) x. f x b. =.
Accelerated Precalculus Graphing exponential and logarithmic functions
Name: ____________________________
f ( x) b x , where b 0, b 1, and x is any real number.
Exponential function with base b:
The graph of the basic exponential function f ( x) b x has the following characteristics: 1. 2. 3. 4.
Reference point: Range: y-intercept: Horizontal asymptote:
(0, 1) (0, ) (0, 1) y0 (0,1)
In addition, the domain is all real numbers. For exponential functions of the form
f ( x) ab xh k 1. 2. 3. 4.
or
f ( x) ab( xh) k
a 0 reflects about the x-axis x reflects about the y-axis h translates the graph left or right (horizontal shift) k translates the graph and the horizontal asymptote up or down (vertical shift)
Examples: Ex. 1: For the following exponential function, find the (1) horizontal asymptote, (2) range, (3) y-intercept, and (4) reference point. Sketch the graph.
f ( x) 2 x1 1. 2. 3. 4.
Because k 0 , the horizontal asymptote is y 0. Because a 1 0 , the graph lies above the horizontal asymptote and the range is (0, ) . f (0) 201 2 , so the y-intercept is (0, 2) . To find the reference point: a. Set the expression in the exponent equal to 0 and solve for x: x 1 0
x 1 b. Sub in this x-value to find the y-coordinate: y 211
y 20 y 1 c. The reference point is (1, 1). 5. Sketch.
Ex. 2: For the following exponential function, find the (1) horizontal asymptote, (2) range, (3) y-intercept, and (4) reference point. Sketch the graph.
f ( x) e2 x 2 1. Because k 2 , the horizontal asymptote is _______________. 2. Because a 1 0 , the graph lies _______________ the horizontal asymptote and the range is _______________. 3. The y-intercept is _______________ or approximately _______________.
4. The reference point is _______________.
5. Sketch.
Logarithmic function with base b: f ( x) logb x , where b 0, b 1, and x 0. The graph of the basic logarithmic function f ( x) logb x has the following characteristics: 1. Reference point: (1, 0) 2. Domain: (0, ) 3. x-intercept: (1, 0) 4. Vertical asymptote: x0 (1, 0) In addition, the range is all real numbers. For logarithmic functions of the form f ( x) a logb ( x h) k or f ( x) a logb [( x h)] k 1. 2. 3. 4.
a 0 reflects about the x-axis x reflects about the y-axis h translates the graph and the vertical asymptote left or right (horizontal shift) k translates the graph up or down (vertical shift)
Examples: Ex. 1: For the following logarithmic function, find the (1) vertical asymptote, (2) domain, (3) x-intercept, and (4) reference point. Sketch the graph. f ( x) log( x 3)
1. To find the vertical asymptote, set the expression in the parentheses equal to 0 and solve for x: x 3 0 so x 3 2. For the domain, the expression in the parentheses must be greater than 0: x 3 0 so x 3 3. To find the x-intercept, let y 0 and solve for x: 0 log( x 3) 100 x 3 1 x3 x 2 4. To find the reference point: a. Set the expression in the parentheses equal to 1 and solve for x: x 3 1 x 2
5. Sketch.
b. Sub in this x-value to find the y-coordinate: y log(2 3) y log1 y0
Ex. 2: For the following logarithmic function, find the (1) vertical asymptote, (2) domain, (3) x-intercept, and (4) reference point. Sketch the graph. y ln(2 x) 1
1. Find the vertical asymptote, ___________________:
2. Find the domain, ____________________________:
3. Find the x-intercept, ______________ or approximately ______________:
4. Find the reference point, _______________________:
5. Sketch.