CCSS.Math.Content.8.EE.C.8
The standard
Analyze and solve pairs of simultaneous linear equations.
Common Core State Standards for Mathematics · Expressions and Equations
What this standard means
Students need to solve two linear equations at the same time and understand what the solution means. They should connect tables, graphs, and equations, and see that the solution is the point where both lines share the same x and y values.
Mastery looks like choosing a useful method, graphing, substitution, or elimination, then checking the ordered pair in both equations. Students often get stuck treating each equation separately, misreading the intersection point, or making sign errors when combining equations.
Ways to teach it
- Have students graph two tape-line equations on grid paper, mark the intersection, and check the point in both original equations.
- Ask students to write: What does the intersection point mean in a word problem about two phone plans?
- Give one system with a proposed solution, and have students verify it by substituting into both equations.
- Compare two taxi fare rules, base fee plus per-mile charge, and find when the total costs are equal.
Plan a lesson for CCSS.Math.Content.8.EE.C.8
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Related standards
- CCSS.Math.Content.8.EE.C.8c
Solve real-world and mathematical problems leading to two linear equations in two variables.
- CCSS.Math.Content.HSA-REI.C.6
Solve systems of linear equations exactly and approximately (e.g., with graphs), focusing on pairs of linear equations in two variables.
- CCSS.Math.Content.8.EE.C
Analyze and solve linear equations and pairs of simultaneous linear equations.
- CCSS.Math.Content.HSA-REI.C
Solve systems of equations