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Learn how to fit linear functions to real data, find lines to approximate data, and model data using linear functions. Explore graphing, calculating slopes and y-intercepts, and creating functions from tables. Practice exercises provided.
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Linear Functions and Models Lesson 2.1
Problems with Data • Real data recorded • Experiment results • Periodic transactions • Problems • Data not always recorded accurately • Actual data may not exactly fit theoretical relationships • In any case … • Possible to use linear (and other) functions to analyze and model the data
Fitting Functions to Data • Consider the data given by this example • Note the plot ofthe data points • Close to beingin a straight line
Finding a Line to Approximate the Data • Draw a line “by eye” • Note slope, y-intercept • Statistical process (least squares method) • Use a computer programsuch as Excel • Use your TI calculator
Graphs of Linear Functions • For the moment, consider the first option Given the graph with tic marks = 1 • Determine • Slope • Y-intercept • A formula for the function • X-intercept (zero of the function)
Graphs of Linear Functions • Slope – use difference quotient • Y-intercept – observe • Write in form • Zero (x-intercept) – what value of x gives a value of 0 for y?
Modeling with Linear Functions • Linear functions will model data when • Physical phenomena and data changes at a constant rate • The constant rate is the slope of the function • Or the m in y = mx + b • The initial value for the data/phenomena is the y-intercept • Or the b in y = mx + b
Modeling with Linear Functions • Ms Snarfblat's SS class is very popular. It started with 7 students and now, 18 months later has grown to 80 students. Assuming constant monthly growth rate, what is a modeling function? • Determine the slope of the function • Determine the y-intercept • Write in the form of y = mx + b
Answer: Creating a Function from a Table • Determine slope by using
Creating a Function from a Table • Now we know slope m = 3/2 • Use this and one ofthe points to determiney-intercept, b • Substitute an orderedpair into y = (3/2)x + b
Creating a Function from a Table • Double check results • Substitute a different ordered pair into the formula • Should give a true statement
Assignment • Lesson 2.1 • Page 71 • Exercises 1 – 35 odd