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Math Help - loads of help on functions needed

  1. #1
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    Exclamation loads of help on functions needed

    ok need some help i just cant seem to do these few questions, and i've left it until the last minute as it has to be in tomorrow! aargh! thanks for the help x

    1) find the inverse and state the domain f(x) = 1 - 2^x , x E R
    Last edited by pop_91; November 3rd 2009 at 10:30 PM.
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  2. #2
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    Hello pop_91
    Quote Originally Posted by pop_91 View Post
    ok need some help i just cant seem to do these few questions, and i've left it until the last minute as it has to be in tomorrow! aargh! thanks for the help x

    1) find the inverse and state the domain f(x) = 1 - 2^x , x E R
    Let y = 1 - 2^x

    Then:
    2^x = 1-y

    \Rightarrow x = \log_2(1-y)
    So the inverse function is:
    f^{-1}(x) = \log_2(1-x)
    I presume the question means the domain of the inverse function. The domain of \log(z) is z>0, so here 1-x>0; i.e. the domain is x<1, x \in \mathbb{R}

    Grandad
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  3. #3
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    thanks so much x
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