Solving Linear Systems of Equations with Elimination (Day 1 of 3)

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Objective

SWBAT solve systems of equations using elimination.

Big Idea

Students will identify zero pair coefficients to solve systems of equations by adding.

Do-Now

10 minutes

I expect my students will complete today's Do Now in 5 minutes. I will then ask two students to come up to the board to show their answers to the class. I will ask that each of these student to solve the system using a different method. I will ask the students not to look at each other's work as they solve. After they finish, I will ask the class to analyze their work to see if the students arrived at the same answer.

Next, I will ask a student will read the objective, "SWBAT solve systems of equations using elimination".

I will ask a few volunteers to define "eliminate", and to give some real-world examples of situations where something is eliminated.

Guided Notes + Practice

30 minutes

Before beginning new material, I will return the Exit Cards from our last class to give students an opportunity to review their responses.

Page One:

Next, the class will follow along with me on their Guided Notes. I will remind students that we already know how to solve systems of equations using graphing and substitution, so the point of today's lesson is to explore a new method. I will ask the students to copy the text below on their notes:

  • Eliminate -->  __To get rid of or take away__.
  • We can solve systems of equations by eliminating a _variable_.
  • In order to eliminate a variable, the   coefficient    MUST form a  zero pair when the equations are added .

Students will practice making a zero pair with addition using the nine problems on their handout. When students get to the third row of problems, I will use the following verbal prompts to guide the class along:

  • Our goal is to make a zero pair, but 5 + 5 ≠ 0.
  • How can we make this equation equal zero?
  • What about the next problem? How can I make the number sentence, 8 + 8 = 0, true?

We will then complete the four systems of equations on the bottom of the page. I will complete example one and two, and the students will complete the two "You Try" problems.

Page Two: 

When my students have learned elimination in the past, they typically struggled the most with identifying which variable to eliminate, and, determining when a system must be modified in order to solve using the elimination method. I have designed this activity to isolate these skills.

Students will use four colored pencils to shade each box with the color the corresponds with what happened when the equations were added together. Students do not need to fully solve the system in order to complete this task.  

Lastly, students will pick six systems to solve on the bottom of their papers using elimination. I will ask that students pick at least one box of each color to solve. We will review the responses as a whole group before moving on to the partner activity.

Partner Practice - Versatiles

30 minutes

Students will practice solving systems of equations using elimination using the ETA Hand to Mind product VersaTiles. Students will match correct responses to the numbered tiles in the black VersaTile case. If you do not have a VersaTiles classroom set, the assignment can still be completed by having students match questions and responses with pencil and paper.

Closing

10 minutes

I will ask a volunteer to summarize what the elimination method is, and how it can be used to solve a system of equations. I will ask the class to identify some common misconceptions that a student might have when learning how to use elimination, and to give some suggestions that would help them. Students will then complete an Exit Card.