Lesson 19
Expanding and Factoring
Lesson Narrative
In grade 6, students worked extensively with the distributive property involving both addition and subtraction, but only with positive coefficients. In the previous lesson, students learned to rewrite subtraction as "adding the opposite" to avoid common pitfalls. In this lesson, students practice using the distributive property to write equivalent expressions when there are rational coefficients. Some of the expressions they will work with are in preparation for understanding combining like terms in terms of the distributive property, coming up in the next lesson. (For example, \(17a-13a\) can be rewritten \(a(17-13)\) using the distributive property, so it is equivalent to \(a \boldcdot 4\) or \(4a.\)
Learning Goals
Teacher Facing
- Apply the distributive property to expand or factor an expression that includes negative coefficients, and explain (orally and using other representations) the reasoning.
- Comprehend the terms “expand” and “factor” (in spoken and written language) in relation to the distributive property.
Student Facing
Let's use the distributive property to write expressions in different ways.
Learning Targets
Student Facing
- I can organize my work when I use the distributive property.
- I can use the distributive property to rewrite expressions with positive and negative numbers.
- I understand that factoring and expanding are words used to describe using the distributive property to write equivalent expressions.
Glossary Entries
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expand
To expand an expression, we use the distributive property to rewrite a product as a sum. The new expression is equivalent to the original expression.
For example, we can expand the expression \(5(4x+7)\) to get the equivalent expression \(20x + 35\).
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factor (an expression)
To factor an expression, we use the distributive property to rewrite a sum as a product. The new expression is equivalent to the original expression.
For example, we can factor the expression \(20x + 35\) to get the equivalent expression \(5(4x+7)\).
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