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Math Help - Inverse Function

  1. #1
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    Inverse Function

    Is the inverse of f(x) = 9-2x^2
    f-1(x) = -sqrt( (9/2) - (x/2) )

    Thanks,
    D.
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  2. #2
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    e^(i*pi)'s Avatar
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    Quote Originally Posted by dboyd435 View Post
    Is the inverse of f(x) = 9-2x^2
    f-1(x) = -sqrt( (9/2) - (x/2) )

    Thanks,
    D.
    The working in your post is correct except I do not see why you can't have a plus or minus infront of that square root unless there is something about the domain you're not telling me

    y = 9-2x^2

    2x^2 = 9-y

    x^2 = \frac{9-y}{2}

    x = \pm \sqrt{\frac{9-y}{2}}

    f^{-1}(x) = \pm \sqrt{\frac{9-x}{2}}

    Bear in mind that's not a function since it's not one to one - the domain would have to be restricted to make it a function. t
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  3. #3
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    Thanks, ya, I meant to put +/- but i guess it didn't type out for some reason.
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