1. Select Show additional function. Graph y = 5(1 + 0.20)t along with y = 5(1 - 0.20)t.

What do the two graphs have in common?

How are the graphs different?

2 . A computer is purchased for $1000 and depreciates (loses value) by 15% each year.

What percent of value does the computer retain each year?

Write function that models the value of the computer after t years. Explain.

3. Use the function y = 98(0.93)t to answer the following questions.

What is the y-intercept of the function?

What is the value of r? Explain.

4. In 2000, the population of Dullville was about 95,000. Over the next decade, the population decreased by 18%. For the questions below, assume this rate of decay will continue.

What function models the population after t decades?

Graph your function in the Gizmo. (Hint: Let y = population in thousands. To enter the initial value, type 95 in the field next to the C slider and hit Enter.) Then select Show probe and drag it to the right. About what will the population be after 30 years (t = 3 decades)?

Roughly when will the population be half the initial population?

5. Use the graph to the right to answer the following questions.

What is the initial value?

What is the percent of change per year?

What function is graphed here? Explain. Check your answer in the Gizmo.

6. Challenge: Consider the graph to the right.

What function is graphed here?

Explain your reasoning.

Check your answer in the Gizmo.

7. Sandra deposits $1500 into an account that earns 2% interest compounded annually.

Write function that models the balance after t years.

What is the balance after 7 years? (Use a calculator.)

Check your answers in the Gizmo. Correct any mistakes as needed. (Hint: The Gizmo allows you to type in values for C from -100 to 100. For this problem, you can enter C = 15 and let y = the balance of the account in hundreds.)

Use the probe to estimate how long it takes for the balance to double.

8. Jason buys a car for $24,000. The car depreciates (loses value) at a rate of 18% each year.

What function models the value of the car after t years?

What is the value of the car after 6 years? (Use a calculator.)

Check your answers in the Gizmo. (Use C = 24.) Fix any mistakes above, if needed.

About when will the car be worth half its initial value? (Use the probe.)

9. Use the graph to the right to answer the following questions.

What is the initial value?

What is the percent of change per year?

What function is graphed here? Explain.