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Homework Help: Basic funtion, just can't figure out one part

  1. Sep 17, 2006 #1
    The problem is this

    A cable television firm presently serves 5000 households and charrges 20 dollars per month. A marketing survey indicates that each decrease of 1 dollar in the monthly charge will result in 500 new customers. Let R(x) denote the total monthly revenue when the monthly charge is x dollars.

    Determine the revenue function R

    The back of the book says

    I don't see where the 30 comes from, can anyone tell me?
  2. jcsd
  3. Sep 17, 2006 #2
    30 is given information. It is obtained by observing that increasing the monthly fee by 10 dollars from 20 would result in 0 households with the service.
  4. Sep 17, 2006 #3
    ah! Thank you. I feel stupid now. how could i overlook that.
  5. Sep 27, 2006 #4
    Well, since my new problem relates to basic functions, I figured I'll just reuse to this topic.

    This isn't exactly homework, but I just have a question.

    Why does (x^2+1)(x-1)/(x^2 + 1)(x-2) not have a hole in the graph despite having a common factor?
  6. Sep 27, 2006 #5


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    Science Advisor

    Because x2+ 1 is never 0.
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