Solving Linear Systems of Equations with Substitution (Day 2 of 3)

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SWBAT solve systems of equations using substitution by solving one equation for a specific variable.

Big Idea

Students will use inverse operations to solve one equation in a system in order to use linear substitution.


10 minutes

Students will be isolating a variable in today's lesson, so today's Do Now gives students an opportunity to practice solving a literal equation. After 5 minutes, I will ask student volunteers to come to the front of the room to show their answers on the board.

Next, I will ask a student will read the objective, "SWBAT solve systems of equations using substitution by solving one equation for a specific variable ". I will ask a volunteer to give a brief summary of what we learned about substitution during our last class.

Guided Notes + Practice

35 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: Students will then complete the Review on the top of today's guided note sheet. I will ask two students to come up to the front of the board to act as the instructor by talking through the process they used to solve the system with substitution and check the solutions for each.

I will ask students to examine the system of equation at the bottom of the paper, and to identify how this system is different than the review problems.  Some of the students will quickly realize that neither equation is solved for a specific variable. How will we know what to substitute?

Students will be prompted to re-examine the review problems that were just completed as a whole group. I will tell students that we were able to easily fill in the red script below each problem because one variable was already isolated, so we immediately knew what our substitution would be. I will then ask the class if we know how to rearrange an equation for a specific variable. At this point, most students will refer to the literal equations that we completed during the Do-Now. 

I will ask students to decide which variable would be easiest to isolate. We will then solve the system using substitution as a whole group.

Page Two: In the past, students have struggled the most with knowing which variable to isolate when solving a system with substitution. Students will practice this individual skill before moving on to fully solve a system. Students will match each system of equation with its corresponding modified equation that can be used as the substitution.

Partner Practice

25 minutes

Students will practice today's objective using this handout. The class will work in pairs on the assignment for 25 minutes.

First, students will verify the correctness of a solution by inputting a given solution into the system itself. This is often skipped when students solve a system on their own, so this handout deliberately opens up with this activity.

I want students to continue to make the connection between the different methods used to solve a system of equation, so students will solve the rest of the systems on their paper graphically and algebraically.


10 minutes

I will ask the students to describe how they would describe today's lesson to a student that was absent or still struggling with substitution. Next, a volunteer will be asked to give a short summary of what we learned in class today. Students will then complete an exit card.