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Learn how to write exponential and power functions passing through given points, solve for variables, and use regression models to make predictions.
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Academy Algebra II 7.7: Write and Apply Exponential and Power Functions
Write an Exponential Function y = abx That Passes Through Two Points. • Write the exponential function passing through (1, 12) and (3, 108). 1.) Substitute the coordinates into: y = abx 12 = ab1 108 = ab3
Write an Exponential Function y = abx That Passes Through Two Points. • Write the exponential function passing through (1, 12) and (3, 108). 2.) Solve for a in the first equation: 12 = ab1 and substitute into the second equation: 108 = ab3 b > 0 in exponential functions.
Write an Exponential Function y = abx That Passes Through Two Points. • Write the exponential function passing through (1, 12) and (3, 108). 3.) Plug in b-value and solve for a.
Write an exponential function y = abx whose graph passes through the given points. 1.) (1, 3), (2, 12)
Write an exponential function y = abx whose graph passes through the given points. 2.) (3, 8), (6, 64)
Write a Power Function y = axb That Passes Through Two Points. • Write the power function passing through (3, 2) and (6, 9). Substitute the coordinates into: y = axb and solve (just like the exponential function). Hint: Use logs.
Write a power function y = axb whose graph passes through the given points. • (2, 1), (7, 6)
Write a power function y = axb whose graph passes through the given points. • (3, 4), (6, 15)
Use Exponential Regression • Find an exponential model for the data. Use the model to predict the number of scooters sold in the 8th year. 89: Graphing Calculator: Select data/matrix editor. Create new or open. Input data (to clear data, press F1 (tools), select 8: clear editor. Turn on plots: Press F2 (plot setup), press F1 (define), fill in c1 and c2 for x and y. 83/84: Graphing Calculator: Press Stat, select edit. Input x in list1 and y in list2. Zoom – select zoomstat to view graph (make sure plot 1 is on: press y = and highlight plot1)
Use Exponential Regression • Find an exponential model for the data. Use the model to predict the number of scooters sold in the 8th year. 89: Graphing Calculator: To view graph, adjust window and press graph. To calculator regression, press F5 (calc), change calculation type to ExpReg, type c1 and c2 for x and y, and store regression to y1(x). 83/84: Graphing Calculator: Press Stat, arrow over to Calc, Arrow down to ExpReg. To view exponential function on graph: Input equation in y1. Press graph.
Use Power Regression • Find a power model for the data. Use the model to predict the weight of a bird with wingspan of 4.5 feet. Input data in just like the previous question. When selecting regression, select: PwrReg.