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

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Objective

SWBAT solve systems of equations using elimination.

Big Idea

Students will use multiplication to create zero pair coefficients. Students will use graphing calculators to verify the solution to a system of equations.

Do-Now

10 minutes

I plan for my students to complete today's Do Now in 5 minutes.  I will then ask three students to come up to the board to show their answers to the class. I will ask that each student solve the system using a different method. 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".

Before moving forward, I will return the graded exit cards to students from our last class. We will review the responses as a whole group.

Review

15 minutes

Using clickers to collect automatic responses, I will review my students' understanding of solving systems of equations using elimination. I have prepared six review questions (slides 2 - 7). Before I begin, I will set a class goal of 80% accuracy on all questions. If the class meets this goal, I will shorten tonight's homework assignment.

Guided Notes + Practice

20 minutes

After the Review, students will continue to follow along with this presentation on Slide 8. Students will take notes using this handout.

I will ask students to examine the system in Example One , and to decide how this system is different that the ones that we have seen up to this point. I will show the class that this problem can also be solved with elimination by multiplying both equations to create a zero pair. 

I will solve Example One twice, eliminating a different variable each time, to show students the freedom that exists when solving a system with consistent multiplication. We will solve Example Two as a whole group twice, and Example Three twice independently. 

I will encourage students who finish early to solve Example Three another way, using multiplication to create two brand new equations.

Partner Practice - Calculators

25 minutes

Students will use the rest of class to practice solving systems of equations using elimination. Students will work on this handout from the Kuta Software website.

Students will have the option to start this assignment at two different places. Students who feel confident solving systems with elimination should start on #9. Students who are still struggling should begin at #1.

Students will use a TI-Nspire calculator to check their solutions as they work on this handout. I will ask students to complete two to three problems at a time, then to stop to check their solution in the calculator before moving forward to the next one. If their solution does not match with the calculators, I will ask students to work in a pair with me or another student to help get them back on the right track.

Closing

10 minutes

I will write the following systems of equations on the board:

 

y = 2x + 4   

y = -4x + 7

 

3x - 2y = 10

5x + 2y = 6

 

4x + 2y = 14

x = 3y

 

Students will be instructed to silently examine each system, and to decide which method they would use to solve it (graphing, substitution, or elimination). I will then conduct a class poll, with students raising a hand to cast a vote. Next, I will call on a few volunteers to share and justify their choices.

Afterwards, I will tell students that there is no correct/incorrect answer, and that they can decide which method to use based on the appearance of the system, as well as their own personal preferences. 

Students will then complete an exit card.