CCSS.Math.Content.HSA-REI.D
The standard
Represent and solve equations and inequalities graphically
Common Core State Standards for Mathematics · High School — Algebra
What this standard means
Students need to connect algebraic solutions to graphs. They should graph equations or inequalities, find intersections, and explain what those points or regions mean. They also need to see approximate solutions when exact algebra is hard, using tables, graphing tools, or hand sketches.
Mastery looks like choosing a useful graphing window, labeling axes, finding intersection points, and checking whether the answer fits the original situation. Students often get stuck reading scale, mixing up x-values and y-values, or thinking a graphing calculator answer is correct without checking.
Ways to teach it
- Hands-on: Give pairs two linear equations on cards, have them graph on grid paper, then place a sticker at the solution point.
- Prompt: Explain how the intersection of two graphs answers the question, using one sentence about x and one about y.
- Quick assessment: Show two graphed inequalities and ask students to shade the solution region and name one point that works.
- Real-world connection: Compare two phone plans with equations, graph both costs, and identify when one plan becomes cheaper.
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Related standards
- CCSS.Math.Content.HSA-REI.B
Solve equations and inequalities in one variable
- CCSS.Math.Content.2.OA.A
Represent and solve problems involving addition and subtraction.
- CCSS.Math.Content.1.OA.A
Represent and solve problems involving addition and subtraction.
- CCSS.Math.Content.6.EE.B
Reason about and solve one-variable equations and inequalities.