The purpose of this lesson is for students to connect linear relationships to functions and to understand that any linear function can be represented by .

In the first activity, students see that a proportional relationship between two quantities can be viewed as a function. They see that either quantity can be chosen as the independent variable and that the only difference in the equation and the graph is the constant of proportionality, which is visible on the graph as the slope of the line through the origin.

In the next activities, students investigate and make connections between linear functions as represented by graphs, descriptions, and by the equation . They interpret the slope of the line as the rate of change of the dependent variable with respect to the independent variable and the vertical intercept of the line as the initial value of the function. Students also compare properties of linear functions represented in different ways to determine, for example, which function has the greater rate of change.

The last activity is optional. Consider using this activity if students need more practice comparing linear functions represented in different ways.