In this lesson, students see that the area model can be generalized to a diagram when the factored expression contains a difference.

Although they have encountered an algebraic approach, students still benefit from drawing diagrams to expand unfamiliar factored expressions. Area diagrams are intuitive for visualizing the product of two sums, but they are less intuitive for visualizing the product when it contains a difference, such as in . Subtraction can be represented by removing parts of a rectangle and finding the area of the remaining region, but this strategy can get complicated when both factors are differences.

Students also learn to use the terms standard form and factored form. When classifying quadratic expressions by their form, students refine their language and thinking about quadratic expressions (MP6).