Curriculum / Math / 8th Grade / Unit 6: Systems of Linear Equations / Lesson 9
Math
Unit 6
8th Grade
Lesson 9 of 11
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Solve systems of linear equations using elimination (linear combinations) by first creating a zero pair.
The core standards covered in this lesson
8.EE.C.8.B — Solve systems of two linear equations in two variables algebraically, and estimate solutions by graphing the equations. Solve simple cases by inspection. For example, 3x + 2y = 5 and 3x + 2y = 6 have no solution because 3x + 2y cannot simultaneously be 5 and 6.
The foundational standards covered in this lesson
8.EE.C.7 — Solve linear equations in one variable.
The essential concepts students need to demonstrate or understand to achieve the lesson objective
Suggestions for teachers to help them teach this lesson
This is the second of two lessons on solving systems using elimination or linear combinations. In Lesson 9, students learn how to multiply one or both equations in order to use this method.
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Problems designed to teach key points of the lesson and guiding questions to help draw out student understanding
Solve the system using the elimination method. What steps do you need to take before you solve?
$${3x-4y=-5}$$
$${-5x+2y=6}$$
$${2x+3y=4}$$
$${3x+4y=8}$$
Jon buys fencing for his yard. He pays $122 for 5 fence posts and 4 fence panels. He pays $570 for 21 fence posts and 20 fence panels.
How much does he pay for 4 fence posts and 3 fence panels?
Fencing from the Summative Assessment Tasks for Middle School is made available through the Mathematics Assessment Project under the CC BY-NC-ND 3.0 license. Copyright © 2007-2015 Mathematics Assessment Resource Service, University of Nottingham. Accessed March 21, 2018, 7:53 p.m..
A set of suggested resources or problem types that teachers can turn into a problem set
Give your students more opportunities to practice the skills in this lesson with a downloadable problem set aligned to the daily objective.
A task that represents the peak thinking of the lesson - mastery will indicate whether or not objective was achieved
An elementary school teacher places an order for 2 copies of a book and 2 dictionaries for a total of $18. A week later, she places another order for 2 more copies of the book and 3 dictionaries for a total of $22. How much does each book and dictionary cost?
Write a system of equations, define your variables, and solve using the elimination method.
An example response to the Target Task at the level of detail expected of the students.
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.
Lesson 8
Lesson 10
Topic A: Analyze & Solve Systems of Equations Graphically
Define a system of linear equations and its solution.
8.EE.C.8.A
Solve systems of linear equations by graphing.
8.EE.C.8.A 8.EE.C.8.B
Classify systems of linear equations as having a unique solution, no solutions, or infinite solutions.
Solve real-world and mathematical problems by graphing systems of linear equations.
8.EE.C.8.C
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Topic B: Analyze & Solve Systems of Equations Algebraically
Solve systems of linear equations using substitution when one equation is already solved for a variable.
8.EE.C.8.B
Solve systems of linear equations using substitution by first solving an equation for a variable.
Solve real-world and mathematical problems using linear systems and substitution.
Solve systems of linear equations using elimination (linear combinations) when there is already a zero pair.
Solve real-world and mathematical problems using systems and any method of solution.
8.EE.C.8.B 8.EE.C.8.C
Model and solve real-world problems using systems of equations.
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