Characterize Exponential Functions

Which of the following functions shows an initial amount of $15 and an increase of 35% each year?

• y = 15(35)^x

• y = 15(1.35)^x

• y = 15(0.35)^x

• y = 35(1.15)^x

Write an equation that models the following situation:
Samantha's hair was known to grow very rapidly. It began at a length of 6 in and grew at a rate of 14% a week.

• y=6(0.14)^x

• y=6(1+14)^x

• y=6(1.14)^x

• y=6(0.86)^x

Identify the initial value:

y = 6.87 (4)^x

• a = 4

• a = 6.87

• a = 3

• a = 1

The function y = 125(1.13)^x represents Mr. Gantz's recent investments where x is measured in years.  Which is NOT true?

• Mr. Gantz initial invested $125

• Mr. Gantz's money grows by 13% per year

• After 4 years Mr. Gantz will have about $203.81

• Mr. Gantz earns more money in year one than in year 5

Does the graph represent an exponential growth or an exponential decay function?

• Exponential Growth

• Exponential Decay

What does the y-intercept of the graph represent?

• The amount of grams the material is gaining.

• The amount of grams the material is losing.

• The amount of grams remaining after so many years.

• The initial amount of grams.

Which of the following is an increasing exponential function whose y-intercept is 50?

• y = 50(.05)^x

• y = 50x - 4

• y = (2)^x + 50

• y = 50(1.4)^x

The amount of ants in a colony, f, that is decaying can be modeled by                         f(x) = 800(.87)^x, where x is the number of days since the decay started. Suppose           f(20) = 49. Which of the following is true?

• After 20 days, there are 49 ants in the colony.

• After 49 days there are 20 ants in the colony.

• The amount of ants times 20 is 49.

• After 20 days the amount of ants remaining decreases by 49.

The amount of downloads for an album on iTunes, g(d), where d is the number of days since the album was first uploaded can be represented as
g(d) = 5^1.5d
How many downloads will the album have after 3 days?

• 125

• 11

• 1398

• 140

The expression 12(1.015)^t models the population of elephants in a wildlife refuge after t years since 1975.
Is the population of elephants increasing or decreasing?

• Increasing

• Decreasing