Solving Systems of Equations Without a Graph

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Objective

Students will be able to solve a system of equations algebraically by substituting one equation into the other in order to have an equation in one variable. Students will become fluent in this algebraic technique and will conceptually understand the reasoning behind using the substitution technique.

Big Idea

I really like this lesson because of the scaffolds that are in place in the beginning of the lesson. The examples are very simple but really force students to think about what it means to "substitute" one thing for another. Then, once the problem becomes

Opening

10 minutes

Direct Instruction

10 minutes

Independent Practice

15 minutes

Closure

5 minutes

Choose one problem from your independent practice and write out in words why you solved it the way you did.  List the steps and a reason for each step"  If some students in your class struggle with writing they can explain their description to you.  This task will determine which students are understanding the substitution method and which students have only memorized the procedure.