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Math Help - probem with function

  1. #1
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    probem with function

    If f(x)= Log(1+x)/(1-x)
    and g(x)= Log(3x+x^3)/(1+3x^2)
    then f(g(x))=??
    the answer is given in the form of f(x)
    HINT if this helps answer is 3f(x)

    Pls help me with this thanks
    Last edited by cnpranav; April 10th 2009 at 12:49 AM.
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  2. #2
    Super Member Showcase_22's Avatar
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    f(x)=log \left( \frac{1+x}{1-x} \right)

    g(x)=log\left( \frac{3x+x^3}{1+3x^2} \right)

    f (g(x))=log \left( \frac{1+g(x)}{1-g(x)} \right)

    f(g(x))=log \left( \frac{1+log\left( \frac{3x+x^3}{1+3x^2} \right)}{1-log\left( \frac{3x+x^3}{1+3x^2} \right)} \right)

    From here it should just be a lot of algebra.
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  3. #3
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    Quote Originally Posted by Showcase_22 View Post
    f(x)=log \left( \frac{1+x}{1-x} \right)

    g(x)=log\left( \frac{3x+x^3}{1+3x^2} \right)

    f (g(x))=log \left( \frac{1+g(x)}{1-g(x)} \right)

    f(g(x))=log \left( \frac{1+log\left( \frac{3x+x^3}{1+3x^2} \right)}{1-log\left( \frac{3x+x^3}{1+3x^2} \right)} \right)

    From here it should just be a lot of algebra.
    Lolz I knw it till here how to proceed next ??
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  4. #4
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    mr fantastic's Avatar
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    Quote Originally Posted by cnpranav View Post
    Lolz I knw it till here how to proceed next ??
    If you knew it to there then you should have posted that fact so that time and effort was not wasted showing you what you could already do.

    I do not see how you can get the so-called answer of 3 f(x) from all this. Unless the question asks for a specific form for the answer to be given in, the question has been answered in post #2.
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  5. #5
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    Exclamation

    Quote Originally Posted by mr fantastic View Post
    If you knew it to there then you should have posted that fact so that time and effort was not wasted showing you what you could already do.

    I do not see how you can get the so-called answer of 3 f(x) from all this. Unless the question asks for a specific form for the answer to be given in, the question has been answered in post #2.
    BUt then there is got to be a way to solve the equation??
    Or is this the end??
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  6. #6
    MHF Contributor
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    Talking

    There is no "equation" to "solve".

    You were asked to compose the functions, and probably then to simplify the resulting expression. That's all.
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