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Math Help - Functions-domains

  1. #1
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    Smile Functions-domains

    i'm asked to find the domain of these problems

    (0,2) (3,5)

    y=5-x

    y= square root x+4

    I know with fun. the domain is all IR, but is there a way to solve the problems?
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by jay123 View Post
    i'm asked to find the domain of these problems

    (0,2) (3,5)

    y=5-x

    y= square root x+4

    I know with fun. the domain is all IR, but is there a way to solve the problems?
    the domain is the set of all inputs for which a function is defined. when written as ordered pairs, the domain is the set of the first elements in the ordered pair.

    For \{ (0,2), (3,5) \} the domain is \{ 0,3 \}
    since those are the first elements of the ordered pairs

    y = 5 - x

    we can input anything for x here. this is a polynomial, and so, the domain is given by: \mbox{dom}f = \mbox{dom}y = \{ x | x \in \mathbb{R} \} = (-\infty, \infty)

    For \sqrt{x + 4} we have a restriction. we can only input the x-values that ensure that what is being square rooted is non-negative. thus we require x + 4 \ge 0

    so what is the domain of the function here?
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