In an earlier lesson, students learned that some functions can be defined with a rule and the rule can be expressed using function notation. In this lesson, students use rules of functions to find the output when the input is given (or to evaluate functions) and to find the input when the output is known (or to solve equations that define functions). They also interpret rules of functions in terms of a situation. Along the way, they practice reasoning quantitatively and abstractly (MP2).
The term linear function is introduced here. In middle school, students learned a relationship between two quantities is linear if one quantity changes at a constant rate relative to the other. Students see that a linear function can be understood in similar terms: a function is linear if the output changes by a constant rate relative to its input.
This lesson includes an optional activity that is designed to enable students to use technology to graph and evaluate functions expressed in function notation. This skill can help to develop students’ understanding of functions and ability to solve problems in this unit and in future units.
Lesson overview
 5.1 Warmup: Make It True (5 minutes)

5.2 Activity: Data Plans (25 minutes)
 Includes "Are you Ready for More?" extension problem

5.3 Optional Activity: Function Notation and Graphing Technology (20 minutes)
 There is a digital applet in this activity.
 Lesson Synthesis
 5.4 Cooldown: A Third Option (5 minutes)
Learning goals:
 Evaluate functions and solve equations given in function notation, either by graphing or by reasoning algebraically.
 Understand linear function as a function whose output changes at a constant rate and whose graph is a line.
 Use technology to graph and evaluate functions given in function notation.
Learning goals (student facing):
 Let’s graph and find the values of some functions.
Learning targets (student facing):
 I can use technology to graph a function given in function notation, and use the graph to find the values of the function.
 I know different ways to find the value of a function and to solve equations written in function notation.
 I know what makes a function a linear function.
Required materials:
 Graphing technology
Required preparation:
 For the optional activity Function Notation and Graphing Technology, acquire devices that can run Desmos (recommended) or other graphing technology.
 It is ideal if each student has their own device. (Desmos is available under Math Tools.)
Glossary:
 linear function  A linear function is a function that has a constant rate of change. Another way to say this is that it grows by equal differences over equal intervals. For example, \(f(x)=4x3\) defines a linear function. Any time \(x\) increases by 1, \(f(x)\) increases by 4.
 Access the complete Algebra 1 Course Glossary.
Standards:
 This lesson builds towards the standards:CCSS.HSFIF.A.2MS.FIF.2MO.A1.IF.A.2CCSS.HSFIF.B.4MS.FIF.4MO.A1.IF.B.3CCSS.HSFIF.C.7MS.FIF.7aMO.A1.IF.C.7
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