Florida B.E.S.T. MA.912.F.3.4

MathGrades 9–12Create new functions from existing functions.

The Standard

Represent the composition of two functions algebraically or in a table. Determine the domain and range of the composite function.

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

Teacher's field guide

What This Standard Means

What Students Need to Do

Students substitute one function’s output into another function and show the result with a formula or input-output table. They find which inputs are allowed and which outputs the combined rule can produce.

What Mastery Looks Like

A student correctly follows the stated order and builds the composite rule or table. They exclude invalid inputs and accurately describe all possible outputs.

Common Misconceptions

Students reverse the order of the functions or add the rules instead of substituting. They use only the inner function’s domain and miss inputs that make the outer function undefined. They may assume the composite has the same range as one original function.

How to Assess It

Exit ticket: Let f(x) = x² and g(x) = x − 3. Write f(g(x)), then state its domain and range.

Lesson moves

Ways to Teach It

  1. Use two sets of function-machine cards so students pass inputs through both machines and record the composite input-output table.

  2. Ask students to test when f(g(x)) and g(f(x)) differ, then explain why order matters.

  3. Have pairs match cards showing a composite rule, value table, domain, and range, then defend each completed set.

  4. Model a store discount followed by sales tax, then set realistic price limits and find the composite output range.

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Printable MA.912.F.3.4 Worksheet

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