# Lesson 9

Working with Signed Numbers

These materials, when encountered before Algebra 1, Unit 6, Lesson 9 support success in that lesson.

### Lesson Narrative

In Algebra 1, students build on the skills from grade 7 involving applying the distributive property when signed numbers are involved and combining like terms. The purpose of this lesson is to revisit, refresh, and practice that grade 7 work in preparation. For example, in Algebra 1, students are expected to expand expressions like $$(x+4)(x-5)$$. In grade 7, they encountered expressions like $$\text-2x(x-5)$$.

### Learning Goals

Teacher Facing

• Practice expanding and factoring using the distributive property (with diagrams for support) with terms that have negative coefficients.
• Recall multiplication of positive and negative numbers.
• Rewrite subtraction expressions as adding the opposite.

### Student Facing

• Let’s work with signed numbers.