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Math Help - Domain help..

  1. #1
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    Domain help..

    What is the domain of each of the following functions?
    1.) f(x) = 3x + 9
    2.) f(x) = (4x^3 + 4) / (x ( x + 2) (x - 1))
    3.) f(x) = x^3 - x^2 + x - 2 EDIT this is minus sorry

    ur going to make this undefined ryt?
    Last edited by ^_^Engineer_Adam^_^; October 14th 2006 at 07:21 PM.
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  2. #2
    TD!
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    You're probably looking for the "maximal domain", i.e. the largest subset of IR for which f(x) is real (so finite).

    You have to 'watch out' for:
    - denominators becoming 0 for some x-value(s).
    - negative expressions under (square) roots.
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  3. #3
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    Help ive tried learning but Visual Calculus - Drill - Domains of Functions
    is different from # 1 and # 3 questions
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  4. #4
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    Quote Originally Posted by ^_^Engineer_Adam^_^ View Post
    What is the domain of each of the following functions?
    1.) f(x) = 3x + 9
    2.) f(x) = (4x^3 + 4) / (x ( x + 2) (x - 1))
    3.) f(x) = x^3 - x^2 + x - 2 ...
    Hi,

    you have to look for those real numbers x for which the function f will give real values.
    As TD! has pointed out there are only a few restrictions. You don't deal with square-roots or logarithms. So the only restriction could be that the denominator becomes zero.

    1.) D = x Є IR that means: no restrictions
    2.) D = x Є IR\{-2, 0, 1} becaus for these numbers the denominator becomes zero
    3.) D= x Є IR that means: no restrictions

    EB
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