Linear Expressions, Equations, and Functions
Overview
Linear Expressions, Equations, and Functions are found throughout the SAT, so it’s very important to be comfortable with all the key aspects of linear functions and equations. In particular, make sure you know these concepts:
 Linear Expressions
 Linear Equations
 Linear Functions
 SlopeIntercept Form
 PointSlope Form
 Slope
 Parallel/Perpendicular Slope
 Evaluating Linear Functions
 Linear Models
Let’s look at each of these in more detail:
Linear Expressions
Linear expressions include a variable whose exponent is 1. Here are some examples of linear expressions:
Be sure you know how to translate a verbal expression into a linear expression like the ones shown above. To see examples of how to do this, click on this link to see a slide show.
Expressions aren’t equations but they are an important component of linear equations. Also, you can add and subtract linear expressions and still have a linear expression. Multiplying or dividing linear expressions will result in a nonlinear expression. Here are some examples:

Linear Equations
Linear equations include a linear expression equal to a number or another linear expression. A linear equation can have one or more variables, but all terms must be linear.
Here are examples of linear equations with one variable.

If you need more practice in solving onevariable equations, click on the following links:
 Solving OneStep Addition Equations
 Solving OneStep Subtraction Equations
 Solving OneStep Multiplication Equations
 Solving OneStep Division Equations
 Solving TwoStep Multiplication and Addition Equations
 Solving TwoStep Multiplication and Subtraction Equations
 Solving TwoStep Division and Addition Equations
 Solving TwoStep Division and Subtraction Equations
Another skill related to equation solving is the ability to rewrite an equation in an equivalent form. See the examples below.

Make sure you are comfortable with the properties of equality and the structure of an equation. For a quick review, click on this link.
Linear Functions
Before studying what a linear function is, make sure you are comfortable with the following concepts, which we will also review:
 What a function is
 Independent variable
 Dependent variable
 Domain
 Range
 Different representations of functions
Brief Review of Functions
What Is a Function? A function is a onetoone mapping of input values (the independent variable) to output values (the dependent variable). Click on this link to see a quick tutorial on what a function is. This slide show goes over the following key points:
 For every input value (x), there is a unique output value, f(x).
 Functions can be represented as equations, tables, and graphs.
 A function machine is a useful visual representation of the input/output nature of functions.
Dependent/Independent Variables. When one variable depends on another, then it is the dependent variable. For example, the faster your speed, the farther you travel. Suppose that speed is represented by the variable s and the distance traveled is represented by the variable d.
Here’s how to describe the relationship between s and d:
The faster the speed, the more distance traveled.
Distance is dependent on speed.
Distance is a function of speed.
d = f(s)
When studying functions, make sure you are comfortable telling the difference between the independent variable and dependent variable. Get comfortable using function notation. To learn more about function notation, click on this link.
Domain and Range. A function shows the relationship between two variables, the independent variable and the dependent variable. The domain is the allowed values for the independent variable. The range is the allowed values for the dependent variable. The domain and range influence what the graph of the function looks like.
For a detailed review of what domain and range are, click on this link to learn more. You’ll see definitions of the terms domain and range, as well as examples of how to find the domain and range for given functions.
Multiple Representations of Functions. We mentioned previously that functions can be represented in different ways. In fact, any function can be represented by an equation, usually f(x) equal to some expression; a table; or a graph. For a detailed review of multiple representations of functions, click on this link, to see a slide show that includes examples of these multiple representations.
SlopeIntercept Form
The most important form of a linear function is the slopeintercept form.
Given the slope, m, and the yintercept, b, for a linear function, you can easily construct the equation and graph of the linear function. To see examples of graphing linear functions in slopeintercept form, click on this link. This slide show also includes a video tutorial.
PointSlope Form
Another method of finding the slopeintercept form involves using the pointslope form. In this case you are given the slope, m, of the line and one set of coordinates, (x, y), on the line. This is what the pointslope form looks like.
To see examples of deriving the linear function using the in pointslope form, click on this link. This slide show tutorial walks you through the process and provides several workedout examples.
A number of SAT questions will test your understanding of linear functions in slopeintercept and pointslope form.

SlopeBased Questions
Some SAT questions rely on your understanding of slope. While the slopeintercept form includes the notion of slope, there are some additional concepts included.
First, let’s review the basics of slope. This is the slope formula:
Given two coordinates, the slope of the line connecting the two points is found using the slope formula.
On the SAT you may be asked about lines that are parallel or lines that are perpendicular. The key to understanding this is the slopeintercept form for parallel and perpendicular lines. Review these definitions:
Basically, lines that are parallel have the same slope. Lines that are perpendicular have slopes that are negative reciprocals. Look at the following examples.
To see examples of finding the equations of parallel and perpendicular lines, click on the following links:

About Media4Math
All of the resources in this overview can be found on Media4Math. Subscribers can download these resources, or create their own slide shows using Slide Show Creator.