# Lesson 2

Representations of Growth and Decay

### Lesson Narrative

This lesson is optional. Its goal is for students to review different representations (descriptions, tables, graphs, equations) of exponential functions encountered in a previous course before they dive into more rigorous work with exponential functions in this unit. Students also evaluate functions at integer input values, including making sense of negative inputs in context. Later in the unit, students will begin looking at evaluating exponential functions at fractional input values, such as an input of $$\frac12$$ to mean 5 years when an input of 1 means 1 decade.

Throughout this lesson, students repeatedly identify how different exponential functions change by equal factors over equal intervals and use this structure to produce tables, graphs, and equations that represent exponential change (MP7).

### Learning Goals

Teacher Facing

• Explain (in writing) the meaning of different constants in an expression representing an exponential function.
• Interpret equations and graphs that represent exponential functions in context.

### Student Facing

• Let’s revisit ways to represent exponential change.

### Student Facing

• I understand that exponential functions change by equal factors over equal intervals.

Building On

Addressing