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Math Help - [SOLVED] domain and range

  1. #1
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    [SOLVED] domain and range

    Domain and Range are my weakness. I have attempted these problems but I am not sure that they are correct could someone check them/tell me how to correct them please?
    Many thanks!
    f(x)=1+(x^2) D: all reals R:[1, inf)

    f(x)=1-(1/x) D: (-inf, 0) R: (0, inf)

    f(x)=sqrt(3x-1) D: (1/3, inf) R: (1/3, inf)

    f(x)=(x^3)-8 D: all reals R: all reals

    f(x)=x/(x-3) D: (-inf, 3) R: (3, inf)

    Also, if i wanted to write the domain as all reals except one do i denote that R-1?
    Last edited by Jhevon; March 11th 2009 at 08:58 PM. Reason: fixed typo
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  2. #2
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    f(x)=x/(x-3) D: (-inf, 3) u (3, inf) R: (-inf, 1) u (1, inf)

    Also, if i wanted to write the domain as all reals except one do i denote that R-1?
    I think you it's like this: R / {the one that doesnt fit}
    e.g. R / {5}
    But I'm not sure.
    Last edited by Jhevon; March 13th 2009 at 02:17 PM. Reason: removed incorrect info.
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  3. #3
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by deathbyproofs View Post
    f(x)=1+(x^2) D: all reals R:[1, inf)
    yes.

    f(x)=1-(1/x) D: (-inf, 0) R: (0, inf)
    Nein,

    D: (-inf, 0) U (0,inf), R: (-inf, 1) U (1, inf)

    f(x)=sqrt(3x-1) D: (1/3, inf) R: (1/3, inf)
    Nein, 1/3 is included in the domain. the range is also wrong.

    D: [1/3, inf), R: [0,inf)

    f(x)=(x^3)-8 D: all reals R: all reals
    yes

    f(x)=x/(x-3) D: (-inf, 3) R: (3, inf)
    Nein,

    D: (-inf, 3) U (3, inf), R: (-inf, 1) U (1, inf)

    Also, if i wanted to write the domain as all reals except one do i denote that R-1?
    you may use this notation, but you would say {1} not just 1. it is a set difference that you are doing. the set of real numbers minus the element of the set {1}

    Quote Originally Posted by metlx View Post
    I think you it's like this: R / {the one that doesnt fit}
    e.g. R / {5}
    But I'm not sure.
    it is "\" not "/"
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