Unit 4, Lesson 13
Solving Systems by Substitution
Integrated Math 1
Preparation
Lesson Narrative
In this lesson, students transition to solving systems algebraically—by substitution—and to reasoning about systems without a context. The lesson activates and builds on what students have learned in grade 8 about solving by substitution. Students see that a system can be solved by replacing a variable with a number or with an expression, and that various substitutions can be done to solve the same system. They also begin to build an awareness of the kinds of systems that are conducive to being solved by substitution.
Students practice looking for and making use of structure as they identify the variables or expressions to substitute and ways to perform substitutions efficiently (MP7).
- Recognize that a system can be efficiently solved by substitution if one variable is already isolated or can be easily isolated.
- Recognize that there are multiple ways to perform substitution to solve a system of equations.
- Solve systems of linear equations by substituting a variable with a number or an expression, and check solutions by substituting them back into the equations.