Chapter 2: Functions — Input, Output, and Change

Learn how functions connect inputs to outputs and prepare for graphs, slope, rates of change, and calculus.

What You Will Practice

In college math, science, and engineering, one quantity often depends on another. A function is a rule that connects an input to an output. This chapter prepares students for function thinking, graphs, rates of change, and calculus.

What Is a Function?
Function Notation
Linear Functions
Slope as Rate of Change
Quadratic Functions
Tables and Graphs

Mini Lesson

1. What Is a Function?

A function is a rule that gives exactly one output for each input.

input → rule → output

Example: If a tool costs $15 per hour to rent, then cost depends on time.

2. Function Notation

Function notation tells you to evaluate the rule at a specific input.

f(x) = 3x + 2

Example: f(2) = 3(2) + 2 = 8

3. Linear Functions and Slope

A linear function changes at a constant rate. That constant rate is the slope.

y = mx + b

Example: A tank filling at 5 liters per minute can be modeled by V(t) = 5t.

4. Quadratic Functions

Quadratic functions do not change at a constant rate. They often appear in motion, acceleration, and curved paths.

h(x) = x²

Example: h(1)=1, h(2)=4, h(3)=9. The outputs grow faster as x increases.

5. Reading Functions from Tables

A table represents a function if each input has exactly one output.

Example: Time 0, 1, 2, 3 seconds and positions 0, 3, 6, 9 meters form a function.

Interactive Functions Practice

Choose a topic and practice with instant feedback. For function equations, type answers like C(t)=15t, d(t)=60t, or y=5x+2.

Typing tip: Do not use spaces. Examples: 8, function, notafunction, C(t)=15t, y=3x+2.
Big idea: Functions are the language of calculus. Once students understand input → output, they can understand change, slope, derivatives, and accumulation more easily.

Mastery Check

Before moving to Book 2 Chapter 3, students should be able to do the following.

Function Meaning

I can explain a function as an input-output rule.

Function Notation

I can evaluate f(x) when given an input value.

Linear Functions

I can identify the constant rate of change in a linear relationship.

Quadratics

I can evaluate a quadratic function and recognize nonlinear growth.

Tables

I can tell whether a table represents a function.

Go to Chapter 3 Back to Book 2