Cogito
Algebra 1 · Chapter 6 · Lesson 1
Exponential Growth and Decay
Multiplying by the same factor, over and over.
10 problems · about 20 minutes · F-LE.A.1, F-LE.A.2, F-IF.C.8
Figure — use these to answer the problems
- Point(2, 4)
Warm-Up Review
From earlier lessons. Loosen up before the new work.
2 problemsFrom “Systems in Context”
x + y = 12 and x − y = 2. What is x?
AnswerFrom “Solving Systems by Graphing”
Slopes 3 and 3, intercepts 1 and 4. How many solutions?
Answer
Warm Up
Straightforward practice. Get the method working first.
4 problemsy = 4 · 2ˣ. What is y when x = 3?
AnswerWhat distinguishes exponential from linear growth?
- A constant ratio between steps, not a constant difference.
- It is faster.
y = 2 · 3ˣ. What is y when x = 3?
Answery = 5 · 2ˣ. What is y when x = 0?
Answer
Build It Up
The same ideas with more to keep track of.
2 problemsA 20% fall each year. The decay factor as a percent?
AnswerDoes an exponential add or multiply each step?
- Multiplies.
- Adds.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsDoubling
y = 3 · 2ˣ. What is y when x = 4?
AnswerThe Factor
A quantity rises 6% each year. What is the growth factor, as a percent of the original?
Answerpercent