Elimination 3 - multiply one equation only

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SWBAT solve linear systems of equations using elimination, Day 3.

Big Idea

Get kids to stand up or sit down as they become fluent in multiplying one equation before using elimination.


10 minutes

The Lesson 5 - 9 Warmup challenges students to use reasoning, rather than process to understanding the solution to a system of equations. The task asks the students to identify the correct partner equation to form a system with a given solution. 

I like this task because it pushes kids to figure out a more efficient way to solve the problem, one that requires a deeper understanding of what a solution to a system of linear equations actually is.  It is NOT efficient to solve each system (four times) to determine if the point (4, -5) is a solution.  Rather, if kids understand that solutions make each of the equations true, all a student has to do is substitute in the coordinates into each equation to determine which one is the correct equation.

I further throw the kids by giving them a ton of space.  This "tricks" them into thinking that this question requires a ton of work... I emphasize that they should not be robots, and should always think before they tackle a problem with a set of procedures.

For a video narrative about how I structure each lesson, and how the warm-up fits in, click here.

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HW68 Elimination 3 - multiply one equation only includes 5 problems. Four are related to this lesson, one is spiraled review.  I also give the kids the answers to the problems.