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Middle Grades Math: Definition of Functions
by Texas Instruments - Action Consequence Lesson

Published on August 31, 2011


  • Students will determine the domain and range of relationships given as a set of ordered pairs.
  • Students will determine whether or not a relationship is a function or not using the definition.
  • Students will verify that relationships are functions or not by examining the relationship graphically and in a table.
  • Students will define, evaluate, and compare functions (CCSS).
  • Students will reason abstractly and quantitatively (CCSS Mathematical Practice).
  • Students will construct viable arguments and critique the reasoning of others (CCSS Mathematical Practice).
  • Students will look for and make use of structure (CCSS Mathematical Practice).


  • relationship
  • input
  • output
  • domain
  • range
  • function

About the Lesson

This lesson involves examining relationships and functions and their inputs, outputs, domains, and ranges.
As a result, students will:

  • Examine a relationship, determine its domain and range, and plot it on a coordinate grid.
  • Examine a relationship in table form with arrows to connect inputs with their given outputs.
  • Learn that a function is a rule that assigns to each input exactly one output and that the graph of a function is the set of ordered pairs consisting of an input and the corresponding output.
  • Students will create their own relationships, one that is a function and one that is not.

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