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Homework Help: Equation troubles

  1. Mar 15, 2006 #1
    hey i am trying to figure out this equation, dont know where to start with it? Would anyone be able to give me any guidence ?

    If f(x) = 2 x - 4 and g(x) = x² - x - 4, work out f(g(3)).


    Any help would be great

    Thank you
     
  2. jcsd
  3. Mar 15, 2006 #2
    the way i do it is:

    x=3
    so looking at your g(x) equation, every time you see an x, substitute in 3 and see what you get. then do the same with the answer of g(x), by putting the answer into f(x) every time you see an x and then doing the arithmetic.

    hope that helps
     
  4. Mar 15, 2006 #3
    So an actual solution would be:

    g(3) = (3)^2 - 3 - 4
    g(3) = 2
    f(g(3)) = f(2)
    f(2) = 2(2) - 4
    f(2) = 0
    f(g(3)) = 0
     
  5. Mar 15, 2006 #4
    Please don't show full solutions, but rather guide the original poster through to arrive at his/her own solution.
     
  6. Mar 16, 2006 #5
    My apologies.
     
  7. Mar 18, 2006 #6
    thank you for your posts, i understand now :)

    lakitu
     
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