Florida B.E.S.T. MA.912.F.3.8

MathGrades 9–12Create new functions from existing functions.

The Standard

Produce an invertible function from a non-invertible function by restricting the domain.

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

Teacher's field guide

What This Standard Means

What Students Need to Do

Students identify a part of a graph where each output comes from only one input. They choose and state a restricted domain, then verify it with the horizontal line test.

What Mastery Looks Like

For f(x) = x², a student can choose x ≥ 0 or x ≤ 0 and explain why either choice works. The student states the restriction clearly and confirms that outputs no longer repeat.

Common Misconceptions

Students may restrict the range instead of the domain. They may choose an interval that still repeats outputs, or think there is only one valid restriction.

How to Assess It

Exit ticket: For f(x) = (x − 2)² − 3, give one domain restriction that makes the function one-to-one. Explain using the horizontal line test.

Lesson moves

Ways to Teach It

  1. Give pairs a printed parabola and sticky notes to cover sections until every horizontal line meets the visible graph at most once.

  2. Ask students to explain why x ≥ 0 works for f(x) = x² and why x ≥ −2 does not.

  3. Run a card sort matching non-invertible graphs with domain restrictions that make each graph one-to-one.

  4. Graph a ball’s height over time, then restrict time to either its rise or fall so each height matches one time.

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Printable MA.912.F.3.8 Worksheet

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