Lesson 1: What is a Function?
Duration of Days: 3
Lesson Objective
Students will understand that a function is a relationship where each input has exactly one output.
• What is a function?
• Does every input have to have an output?
• Can one input have two different outputs?
• Where do we see functions in real life?
Function, input, output, relationship, rule, machine
CCSS.MATH.8.F.A.1
Description: Functions are introduced as "function machines" that take an input, apply a rule, and produce an output. Using visual representations and manipulatives, students explore that each input produces exactly one output. Real-world examples (vending machines, recipes) make the concept concrete. Purpose: To establish the foundational concept that functions are predictable relationships. DOK Level: 1-2 (Recall and Understanding)
• Visual metaphor: Use actual "function machine" boxes or drawings
• For struggling learners: Use only simple rules (add 1, add 2)
• For advanced learners: Introduce two-step rules
• Kinesthetic: Students become the function machine, receiving input cards and producing output
• Observation: Do students understand one input = one output?
• Worksheet: Given input, find output for 5 examples
• Draw-your-own: Create a function machine with a rule
• Exit ticket: Explain what a function is in their own words
• Function machine visual (box diagram)
• Input/output cards
• Real-world function examples (vending machine, recipe)
• Practice worksheets
• Resource: Khan Academy "What is a Function?" (adapted)