Florida B.E.S.T. MA.912.LT.5.2

MathGrades 9–12Apply properties from Set Theory to solve problems.

The Standard

Given a relation on two sets, determine whether the relation is a function, determine the inverse of the relation if it exists and identify if the relation is bijective.

Florida B.E.S.T. Standards for Mathematics

Teacher's field guide

What This Standard Means

What Students Need to Do

Students decide whether a relation assigns exactly one output to every input. They reverse input-output pairs to form the inverse relation and check whether that inverse is a function. They decide whether the original function is both one-to-one and onto.

What Mastery Looks Like

A student can inspect ordered pairs, a table, or a mapping diagram and justify whether each input has exactly one output. The student reverses every pair and checks whether the result is also a function. The student identifies a bijection by showing that every output is used exactly once.

Common Misconceptions

Students often think repeated outputs mean a relation is not a function, even though only repeated inputs with different outputs cause failure. They may change signs instead of swapping coordinates when finding an inverse. They also confuse one-to-one with onto, especially when unused codomain values are shown.

How to Assess It

Use this exit ticket: Let A = {1, 2, 3}, B = {a, b, c}, and R = {(1, b), (2, c), (3, a)}; classify R, write its inverse, and justify whether it is bijective.

Lesson moves

Ways to Teach It

  1. Give students input and output cards to build mappings, reverse every arrow, and test whether each direction is a function.

  2. Have students answer the prompt “Can a many-to-one function have an inverse function?” using a mapping diagram and counterexample.

  3. Run a card sort where teams classify relations as not a function, function only, or bijection, then justify one choice.

  4. Model employee ID assignments to explain why each employee needs one ID and why unique, fully used IDs make a bijection.

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