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-   -   How I find the Domain definition (https://www.askmehelpdesk.com/showthread.php?t=533687)

  • Dec 11, 2010, 07:47 AM
    pop000
    how i find the Domain definition
    I need to find the Domain definition of this Function:1/x^4-3x^3+9x^2-7

    thanks.
  • Dec 11, 2010, 10:06 AM
    galactus

    You have written:

    .

    I assume you mean:



    This is why grouping symbols are important.
  • Dec 11, 2010, 11:10 AM
    pop000
    Comment on galactus's post
    Yes this what I mean so how I find the Domain definition?

    Thanks
  • Dec 11, 2010, 11:21 AM
    galactus


    Which one? You did not say. I assume that latter? Does find the 'Domain definition' mean find the domain?

    If so:

    Factor the denominator. Set the factors equal to 0 and solve for x.

    These are the values NOT in the domain because they result in division

    by 0.

    This particular quartic has 2 real and 2 complex roots. I assume you are

    not dealing with the complex so find the two real roots.

    Graph it and you can see the vertical asymptotes. That is where there is

    division by 0 and not in the domain.
  • Dec 12, 2010, 01:46 AM
    pop000
    Comment on galactus's post
    I mean the second Equation but is not 7 is need to be 7x
  • Dec 12, 2010, 01:58 AM
    galactus

    Is this correct?:



    If so, factor:



    Set each factor to 0. x=0 is one solution, x=1 is another.
    The remaining quadratic has complex roots.

    The values x=0 and x=1 are NOT in the domain because they give division by 0.
  • Dec 12, 2010, 07:44 AM
    pop000
    Comment on galactus's post
    Thank you for helping now I understand:)

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