1. Here is a graph representing an exponential function, . The function, , gives the value of a computer, in dollars, as a function of time, , measured in years since the time of purchase.

   

   Graph of a decreasing exponential function, x y plane, origin O. Horizontal axis, scale 0 to 4, by 2’s. Vertical axis, scale 0 to 400, by 200’s. The function starts at the vertical axis at (0 comma 400) and goes through (2 comma 100) and (4 comma 25).  

   Based on the graph, what can you say about the following?

   1. The purchase price of the computer
   2. The value of when is 1
   3. The meaning of
   4. How the value of the computer is changing each year
   5. An equation that defines
   6. Whether the value of will reach 0 after 10 years

2. Here are graphs of two exponential functions. For each, write an equation that defines the function, and find the value of the function when is 5.

   1.  

      

      Graph of an increasing exponential function, x y plane, origin O. Horizontal axis, scale negative 4 to 4, by 2’s. Vertical axis, scale 0 to 40, by 20’s. The function starts above the horizontal axis near x equals negative 3 and goes through (0 comma 5), (1 comma 15) and (2 comma 45).  

   2.  

      

      Graph of a decreasing exponential function, x y plane, origin O. Horizontal axis, scale negative 4 to 4, by 2’s. Vertical axis, scale 0 to 40, by 20’s. The function decreases through (negative 1  comma 5), (0 comma 20) and (2 comma 5).

Here are graphs representing two functions, and descriptions of two functions.

Graph of two exponential functions, origin O. Horizontal axis, time(months). Vertical axis, area (square inches). The functions are growing exponentially. The red function has a higher start on the vertical axis than the green function. They meet at point (p comma q) and then the red function ends lower than the green function. 

• Function : The area of a wall that is covered by Mold A, in square inches, doubling every month.
• Function : The area of a wall that is covered by Mold B, in square inches, tripling every month.

1. Which graph represents each function? Label the graphs accordingly and explain your reasoning.
2. When the mold was first spotted and measured, was there more of Mold A or Mold B? Explain how you know.
3. What does the point tell us in this situation?