Linear Expressions & Single-Variable Equations/Inequalities

Lesson 1

Math

Unit 3

9th Grade

Lesson 1 of 12

Objective


Identify properties of operations that result in equivalent linear expressions.

Common Core Standards


Core Standards

  • A.REI.A.1 — Explain each step in solving a simple equation as following from the equality of numbers asserted at the previous step, starting from the assumption that the original equation has a solution. Construct a viable argument to justify a solution method.
  • A.SSE.A.1 — Interpret expressions that represent a quantity in terms of its context 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.
  • A.SSE.A.2 — Use the structure of an expression to identify ways to rewrite it. For example, see x4 — y4 as (x²)² — (y²)², thus recognizing it as a difference of squares that can be factored as (x² — y²)(x² + y²).

Foundational Standards

  • 7.EE.A.1
  • 8.EE.C.7.A

Criteria for Success


  1. Identify and apply the commutative, associative, and distributive properties in expressions. 
  2. Describe that for two expressions to be equivalent, they must be equivalent for ALL values of x, not just one value of x.
  3. Transform an expression, one step at a time, into an equivalent expression. 
  4. Identify and correct incorrect steps taken to transform an algebraic expression. 
  5. Use appropriate vocabulary to describe components of expressions and equations.

Tips for Teachers


  • This lesson builds on and reviews material on the number of solutions of equations in the 8th grade course (8.EE.7a) as well as properties of operations in the 7th grade course (7.EE.1).
  • This article from Dr. Math describes the distinction between “equal” and “equivalent."
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Anchor Problems


Problem 1

Explain how you know the expressions in Column A are equivalent to the expressions in Column B.

Column A Column B
$${-3(x+4)}$$ $${-3x-12}$$
$${(4+x)+3}$$ $${x+(4+3)}$$
$${(x+4)-3}$$ $${-3+(x+4)}$$

 

Guiding Questions

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Problem 2

Explain the properties of operations that were used to transform $${a(x-y)}$$ to the equivalent expression, $${-(ay-ax)}$$.

Guiding Questions

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Problem 3

If the expression$${\frac{x}{2} + \frac{3}{4}}$$ is multiplied by $$4$$, the expression $${{2x+3}}$$ results. 

 

Is $${{2x+3}}$$ an equivalent expression to $${\frac{x}{2} + \frac{3}{4}}$$?

Guiding Questions

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References

Illustrative Mathematics Equivalent Expressions?

Equivalent Expressions?, accessed on Aug. 30, 2017, 4:20 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.

Problem Set


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

Target Task


Are the following two expressions equivalent? Explain your reasoning using the properties of operations. Provide examples to support your reasoning. 

Expression 1: $${(x-y)-z }$$

Expression 2: $${x-(y-z)}$$

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 where you give students a property and then ask them to write an expression using that property.
  • Include problems where students are given two expressions that are not equivalent, and ask to determine using the properties of operations why the two expressions are not equivalent.
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Lesson 2

Lesson Map

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

Topic A: Properties and Solutions of Single-Variable Linear Expressions and Equations

Topic B: Modeling with Single-Variable Linear Equations

Topic C: Properties and Solutions of Single-Variable Linear Inequalities

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