Functions and Transformations

Lesson 1

Math

Unit 5

9th Grade

Lesson 1 of 16

Objective


Write equations and graph linear relationships with different domains.

Common Core Standards


Core Standards

  • A.CED.A.1 — Create equations and inequalities in one variable and use them to solve problems. Include equations arising from linear and quadratic functions, and simple rational and exponential functions.
  • A.CED.A.2 — Create equations in two or more variables to represent relationships between quantities; graph equations on coordinate axes with labels and scales.
  • A.CED.A.3 — Represent constraints by equations or inequalities, and by systems of equations and/or inequalities, and interpret solutions as viable or nonviable options in a modeling context. For example, represent inequalities describing nutritional and cost constraints on combinations of different foods.
  • F.IF.B.5 — Relate the domain of a function to its graph and, where applicable, to the quantitative relationship it describes. For example, if the function h(n) gives the number of person-hours it takes to assemble n engines in a factory, then the positive integers would be an appropriate domain for the function. Modeling is best interpreted not as a collection of isolated topics but in relation to other standards. Making mathematical models is a Standard for Mathematical Practice, and specific modeling standards appear throughout the high school standards indicated by a star symbol (★). The star symbol sometimes appears on the heading for a group of standards; in that case, it should be understood to apply to all standards in that group.
  • F.IF.C.7 — Graph functions expressed symbolically and show key features of the graph, by hand in simple cases and using technology for more complicated cases. Modeling is best interpreted not as a collection of isolated topics but in relation to other standards. Making mathematical models is a Standard for Mathematical Practice, and specific modeling standards appear throughout the high school standards indicated by a star symbol (★). The star symbol sometimes appears on the heading for a group of standards; in that case, it should be understood to apply to all standards in that group.

Foundational Standards

  • 8.EE.B.5
  • 8.EE.B.6
  • 8.F.B.4

Criteria for Success


  1. Write equations to represent descriptions of graphs without context.
  2. Describe how a graph changes based on the domain of the equation.
  3. Write equations to represent contextual situations.
  4. Graph relationships in contextual situations, taking into account the domain described by the situation.

Tips for Teachers


This lesson serves to introduce the concept of linear piecewise functions, reviewing skills and concepts from Unit 1 that will be needed in the next few lessons.

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Anchor Problems

25-30 minutes


Problem 1

Recall the aquarium problem from Unit 1, Lesson 7. In the aquarium below, there are four possibilities that affect the water level: turning the faucet on and off, inserting or removing a plug, adding or removing a rock, or using a bucket to add or remove water. The graph below shows the height of water in the aquarium over a 17-minute interval.

          

  1. Write a linear equation to represent each section of the graph over the time interval $${0≤t≤10}$$ minutes.
  2. Compare the slopes of your equations for the domains $${ 0≤t<2}$$ and $${2≤t<5}$$. What does this mean in context of the situation?
  3. Extend the graph to include the following additional events:
  • Add a bucket of water and turn the faucet on for 2 minutes (assume the plug is in).
  • Turn the water off and let it sit for 1 minute.
  • Pull the plug for 1 minute.

Guiding Questions

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References

Illustrative Mathematics The Aquarium

The Aquarium, accessed on June 22, 2017, 1:09 p.m., is licensed by Illustrative Mathematics under either the CC BY 4.0 or CC BY-NC-SA 4.0. For further information, contact Illustrative Mathematics.

Modified by Fishtank Learning, Inc.

Problem 2

A function is described below.

  • Over the domain $${x≤2}$$, the graph is a linear function passing through the point $${(-2, 1)}$$ with a slope of $${{3\over2}}$$.
  • Over the domain $${2<x≤5}$$, the graph represents a constant value of $$7$$.
  • Over the domain $${x>5}$$, the graph is a linear function passing through the points $${(6, 4) }$$ and $${(8, -2)}$$.
  1. Write an equation to represent each section of the graph.
  2. Draw the graph in the coordinate plane. 

Guiding Questions

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Problem Set

15-20 minutes


Give your students more opportunities to practice the skills in this lesson with a downloadable problem set aligned to the daily objective.

Target Task

5-10 minutes


A store is having a sale to clear out merchandise. If you spend between $0 and $100, you can take 15% off of your total. If you spend over $100, you can take 25% off of your total. 

  1. Write an equation to represent your discounted total if you spend between $0 and $100. 
  2. Write an equation to represent your discounted total if you spend over $100.
  3. Which graph best represents the situation?

Additional Practice


The following resources include problems and activities aligned to the objective of the lesson that can be used for additional practice or to create your own problem set.

  • Include problems similar to Anchor Problem 2 (without context) and the Target Task (with context)

Next

Graph piecewise functions presented algebraically and write piecewise functions from graphs.

Lesson 2
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Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Piecewise Functions

Topic B: Absolute Value Functions

Topic C: Function Transformations

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