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Homework Help: Function Problem

  1. Dec 1, 2008 #1
    1. The problem statement, all variables and given/known data

    Express the area of a rectangle with the perimeter of 100 feet as a function of the lengh L of one of its sides


    2. Relevant equations
    100=2w+2l


    3. The attempt at a solution
    As far as I can get is,

    L = 50 -2w

    Just writing the function is a problem, I assume it's something like but I'm not sure, sorry if I'm completely off it's been a long day.
    A(W) = (50-2w)(w) = 50w - 2w^2
    or
    A = w(50-w)
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Dec 1, 2008 #2

    symbolipoint

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    Education Advisor
    Gold Member

    You successfully wrote the function for area (in two equivalent forms).
     
  4. Dec 1, 2008 #3

    Mentallic

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    Homework Helper

    If [tex]100=2L+2W[/tex]

    then [tex]L=50-W[/tex] but [tex]L\neq 50-2W[/tex]

    Therefore your 2nd equation for the function is the correct one. [tex]A=-W^2+50W[/tex]

    But the question asked as a function of the length, not width. It will be similar though. Just make width the subject of the perimeter equation and substitute into the area formula.
     
    Last edited: Dec 1, 2008
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