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Math Help - image and pre-image of a function/interval

  1. #1
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    aberdeen
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    image and pre-image of a function/interval

    Hi,
    I'm having a problem with setting the image of a function or interval of a function.
    I do understand how to calculate the pre-image.
    Example:
    f(x) = -x^2 - 3

    so to calculate the pre-image of the interval (0,1) I simply calculate 0 = -x^2 - 3 and I get minus square root of 3 and square root of 3,
    and 1 = -x^2 - 3 and I get minus square root of 2 and square root of 2.

    1) how to calculate the image of the function?
    2)image of the interval (-1,3)?
    3) and why is the pre-image of the interval (3,10) = 0 and (3,4) = ?

    Thx
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  2. #2
    MHF Contributor

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    Re: image and pre-image of a function/interval

    Quote Originally Posted by misqa88 View Post
    Example:
    f(x) = -x^2 - 3
    so to calculate the pre-image of the interval (0,1) I simply calculate 0 = -x^2 - 3 and I get minus square root of 3 and square root of 3,
    and 1 = -x^2 - 3 and I get minus square root of 2 and square root of 2.
    1) how to calculate the image of the function?
    2)image of the interval (-1,3)?
    3) and why is the pre-image of the interval (3,10) = 0 and (3,4) =

    I have read several of your post. I can suggest that you use a graphing calculator, a computer algebra or use this website.

    Look long and hard at the graph. Then try to answer your questions.
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  3. #3
    Newbie
    Joined
    Oct 2012
    From
    aberdeen
    Posts
    22

    Re: image and pre-image of a function/interval

    The worst is I can read it from the graph but I don't know how to calculate it without one...
    1) f= (-∞,3)
    2) f(-1,3) = (-6,3)
    I will have no time for drawing graphs for every single function on my test that's why I was looking for some help.
    Thx
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