Mississippi Math FA.F.13

MathGrades 9–12Functions (F) Functions

The Standard

Compare and contrast a function and a relation. Use appropriate strategies to assess whether a given situation represents a function or a relation (e.g., the vertical line test).

2025 Mississippi College- and Career-Readiness Standards for Mathematics

Teacher's field guide

What This Standard Means

What Students Need to Do: Students decide whether each input has exactly one output in ordered pairs, tables, graphs, and everyday situations. They use the vertical line test on graphs and know that every function is a relation.
What Mastery Looks Like: Students can spot one input paired with two different outputs, even when the pairs are far apart in a table. They explain why two inputs may share an output and use a vertical line to check a graph.
Common Misconceptions: Students may think two inputs sharing an output breaks a function. Some use a horizontal line test or assume a relation cannot also be a function.
How to Assess It: Exit ticket: Is {(1,4), (2,4), (1,5)} a function? Is the graph of y=3 a function? Explain both answers.

Lesson moves

Ways to Teach It

Give students cards with (1,2), (1,5), and (2,3); have them plot the points on graph paper and check with a ruler.
Ask students to explain why (1,2) and (3,2) can belong to a function, but (1,2) and (1,5) cannot.
Play function or not: teams sort a conflicting-output table, shared-output mapping, x=2 graph, and y=x graph, then defend their labels.
Have students list classmates and their assigned homerooms, then classmates and their clubs; identify which list gives one output per student.

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