# Lesson Plan: Expanding an Expression to a Difference of Two Squares Mathematics • 9th Grade

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to multiply the sum of two terms by their difference to get the polynomial known as the difference of two squares.

#### Objectives

Students will be able to

• recall and apply the formula of the difference of two squares to expand a product of a sum and a difference,
• understand geometrically why a difference of two squares is the product of a sum and difference,
• find the value of an unknown using the formula of the difference of two squares.

#### Prerequisites

Students should already be familiar with

• multiplying binomials vertically and horizontally and using the FOIL method,
• laws of exponents.

#### Exclusions

Students will not cover

• expanding a product that is not a difference of two squares,
• operations on polynomials other than the product that is a difference of two squares,
• factoring using the difference of two squares.