# Lesson 20

Quadratics and Irrationals

These materials, when encountered before Algebra 1, Unit 7, Lesson 20 support success in that lesson.

### Lesson Narrative

In this lesson, students get familiar with rational and irrational numbers by considering some of the properties of rational numbers and approximating a decimal value for some irrational numbers. In the associated Algebra 1 lesson, students examine irrational solutions to quadratic equations. Students are supported in that work by familiarizing themselves with rational and irrational numbers. Students have the opportunity to look for regularity in repeated reasoning (MP8) when they are asked about properties of rational numbers.

### Learning Goals

Teacher Facing

- Approximate irrational numbers by examining nearby rational values.
- Recall that rational numbers have decimal representations that either terminate or repeat.

### Student Facing

- Let’s explore irrational numbers.

### CCSS Standards

Building Towards