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Math Help - f(x) g(x) help

  1. #1
    Newbie
    Joined
    May 2008
    Posts
    13

    f(x) g(x) help

    Question
    If f(x) = 4x - 12, and g(x) = x^2 + 12, what is f(g(x))?

    Work Done
    4(x^2 + 12) - 12
    4x^2 + 48 - 12
    4x^2 + 36

    Is this coorect? I substituted g(x) in the f(x) equation when there was an x.
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  2. #2
    Super Member
    Joined
    Oct 2007
    From
    London / Cambridge
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    591
    Quote Originally Posted by Alan View Post
    Question
    If f(x) = 4x - 12, and g(x) = x^2 + 12, what is f(g(x))?

    Work Done
    4(x^2 + 12) - 12
    4x^2 + 48 - 12
    4x^2 + 36

    Is this coorect? I substituted g(x) in the f(x) equation when there was an x.
    That's perfect, Well done.

    Here is a harder question for you to try.

    f(x) = \frac{x+3}{x-4} and g(x) = \frac{x-1}{x+2}

    show that g(f(x)) = \frac{7}{3x-5}

    Bobak
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  3. #3
    Newbie
    Joined
    May 2008
    Posts
    13
    Thanks, I'll probably have some more questions soon. I am reviewing for an exam.
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