Introduction to Functions
Abstract
This lesson is designed to introduce students to the idea of functions
and their representations as rules and data tables, including the mathematical notions of independent and dependent variables.
Objectives
Upon completion of this lesson, students will:
 have been introduced to functions
 have learned the terminology used with functions
 have practiced describing functions with one operation
in English sentences, data tables, and with simple algebraic expressions.
Standards
The activities and discussions in this lesson address the following
NCTM standards:
Algebra
Understand patterns, relationships and functions
 represent, analyze, and generalize a variety of patterns with tables, graphs, words, and,
when possible, symbolic rules;
 relate and compare different forms of representation for a relationship;
 identify functions as linear or nonlinear and contrast their properties from tables, graphs,
or equations.
Represent and analyze mathematical situations and structures using algebraic symbols.
 develop an initial conceptual understanding of different uses of variables;
 explore relationships between symbolic expressions and graphs of lines, paying particular
attention to the meaning of intercept and slope;
 use symbolic algebra to represent situations and to solve problems, especially those that
involve linear relationships;
 recognize and generate equivalent forms for simple algebraic expressions and solve linear
equations
use mathematical models to represent and understamd quantitative relationships
 model and solve contextualized problems using various representations, such as graphs,
tables, and equations
Analyze change in various contexts
 use graphs to analyze the nature of changes in quantities in linear relationships.
Student Prerequisites
 Arithmetic: Students must be able to:
 perform integer and fractional arithmetic
 Technological: Students must be able to:
 perform basic mouse manipulations such as point, click and drag
 use a browser such as Netscape for experimenting with the activities
Teacher Preparation
Students will need:
 Access to a browser
 pencil and paper
 Copies of supplemental materials for the activities:
Key Terms
This lesson introduces students to the following terms through the included discussions:
Lesson Outline
These activities can be done individually or in teams of as many as four students.
Allow for 23 hours of class time for the entire lesson if all portions
are done in class.
 Focus and Review
Remind students what has been learned in previous lessons that will be pertinent to this lesson and/or
have them begin to think about the words and ideas of this lesson:
 Objectives
Let the students know what it is they will be doing and learning today. Say something like
this:
 Today, class, we are going to learn about functions and their representations.
 We are going to use the computers to learn about functions and their representations,
but please do not turn your computers on until I ask you to. I want to show you a little about
this activity first.
 Teacher Input
 Introduce the idea of functions as machines, by leading a class
discussion on functions.
 Guided Practice
 Independent Practice
 Have the students practice their new function building and pattern recognition skills with
the Function Machine Game.
Be sure to have students record how many numbers they needed to look at before
correctly guessing the function structure. Have them write the functions they worked with in
three ways:
 English sentence
 Table of values
 Algebra rule
 Have them try to think of situations in
their lives that might be governed by
some of the functions they worked with. For example,
y = x + 1
might be the function
describing growing one year older on your birthday. y = 2 * x
might be the function "everything tastes twice as good during the holiday."
 Closure
 You may wish to bring the class back together for a discussion of the findings.
Once the students have been allowed to share what they found, summarize the results of
the lesson.
Alternate Outlines
This lesson can be rearranged in several ways.
 Add a "name that function" contest (modeled on name that tune) in which teams of students compete to figure out the function. Here is a set of possible
rules for such a game:
 Show two input/output pairs to both teams  two students on a team works very well.
 Have each team state how many more pairs they think that they would need to see to "name that function." The team who claims the fewest needed pairs goes first.
 If a team guesses wrong the other team gets to try, after seeing one more pair. Teams alternate turns until one guesses correctly.
This game can be played in about 10 minutes per pair of teams, making it time consuming if the entire class is to have a turn.
 Introduce nonlinear functions by allowing exponentiation (whole numbers to start) and division by x.
Suggested FollowUp
After these discussions and activities, students will have an intuitive
understanding of functions and will have seen many examples of linear
functions. The next lesson
More Complicated Functions will introduce students
more general linear functions.
