9.1 Exponential Functions
Exponential Functions A function of the form y=abx, where a=0, b>0 and b=1. Characteristics 1. continuous and one-to-one 2. domain is the set of all real numbers 3. Range is either all real positive numbers or all real negative numbers depending on whether a is < or > 0 4. x-axis is a horizontal asymptote 5.y-intercept is at a 6. y=abx and y=a(1/b)x are reflections across the y-axis
Example 1 Sketch the graph of y=2x. State the domain and range.
Example 2 Sketch y=( 1 2 )x. State the domain and range.
Exponential Growth & Decay Exponential function with base greater than one. y=2(3x) Exponential Decay: Exponential function with base between 0 and 1 y=4(1/3)x
Example 3-6 Determine if each function is exponential growth or decay y=(1/5)x y=7(1.2)x y=2(5)x y=10(4/3)x
Steps to write an exponential function 1. Use the y-intercept to find a 2. Choose a second point on the graph to substitute into the equation for x and y. Solve for b. 3. Write your equation in terms of y=abx (plug in a and b)
Example 7 Write an exponential function using the points (0, 3) and (-1, 6)
Example 8 Write an exponential function using the points (0, -18) and (-2, -2)
Example 9 In 2000, the population of Phoenix was 1,321,045 and it increased to 1,331,391 in 2004. A. Write an exponential function of the form y=abx that could be used to model the population y of Phoenix. Write the function in terms of x, the number of years since 2000. B. Suppose the population of Phoenix continues to increase at the same rate. Estimate the population in 2015.
Exponential Equations An equation in which the variables are exponents Property of Equality If the base is a number other than 1 and the base is the same , then the two exponents equal each other. 2x = 28 then x=8
Steps to Solve Exponential Equations/inequalities 1. Rewrite the equation so all terms have like bases (you may need to use negative exponents) 2. Set the exponents equal to each other 3. Solve 4. Plug x back in to the original equation to make sure the answer works
Example 10 Solve 32n+1 = 81
Example 11 Solve 35x = 92x-1
Example 12 Solve 42x = 8x-1
Example 13 Solve
Example 14 Solve
Example 15 Solve