Transformations of graphs
Competing phone companies

The functions represented in the tool below describe the rates charged by two competing cellular phone companies. Each company has a fixed charge for each minute. One of the companies also charges a basic monthly fee. Each company wants to draw away customers from its competitor by announcing a rate reduction.


Use words to describe the rates of each of the companies.
  • Describe the customers that will prefer one or the other company based on current rates.
  • The first company announced a special "free time" offer. In the month of January, the company will offer 20 minutes of free time. (Customers who use the phone for 30 minutes during the month will pay only for 10 minutes.)

    - Use the tool below to change the function describing the rate of the first company so that it takes into account the "free time" during January.
    - What transformation needs to be performed on the graph to describe the rate when a "free time" offer is made during any month?
    - What is the amount of free time you recommend the first company to offer if it wants to attract all the customers who use their cell phones for up to 5 hours per month?


  • In reaction to the first company's "free time" offer, the second company announced that it would reduce its basic monthly fee.
    - What transformation needs to be performed on the graph to describe a reduction in the basic monthly fee?
    - By how much should the second company reduce its basic monthly fee in order to bring back the customers it lost to the first company becuase of that company's "free time" offer?


  • How much will the customers of the two companies gain from the two reductions?


  • table step
    grid
    graph width
    monthly bill (dollars)
    minutes
    f1
    f2
    translations
    translation size
    trace






    Translations and reflections
    Translations of lines through the origin

    Translating lines
    Different ways to translate
    Competing phone companies
    Tag
    Stories about rides
    Bike ride
    Plans for a trip
    Motorcycle and busses

    Exercise 1
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    Exercise 9