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Math Help - Equalities -Need Help

  1. #1
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    Equalities -Need Help

    Hi,

    I'm curious about the question below. I felt that answer should be (a). Anyone knows?

    If |a|<4 and |b|>9, then the best we can say about |a-b| is that?
    (a) |a-b|<-5
    (b) |a-b| > 5
    (c) |a-b| <5
    (d) |a-b| >13

    Thanks loads,
    weijing
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  2. #2
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    Re: Equalities -Need Help

    Quote Originally Posted by weijing85 View Post
    Hi,

    I'm curious about the question below. I felt that answer should be (a). Anyone knows?

    If |a|<4 and |b|>9, then the best we can say about |a-b| is that?
    (a) |a-b|<-5
    (b) |a-b| > 5
    (c) |a-b| <5
    (d) |a-b| >13

    Thanks loads,
    weijing
    An absolute value is allways positive or zero. So a) is definitely not a solution to your question.

    To find the answer to the question use the numberline.
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  3. #3
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    Re: Equalities -Need Help

    Quote Originally Posted by weijing85 View Post
    If |a|<4 and |b|>9, then the best we can say about |a-b| is that?
    (a) |a-b|<-5 (b) |a-b| > 5 (c) |a-b| <5 (d) |a-b| >13
    You have been told that it cannot be a).

    Recall that |a-b| is the distance between a~\&~b.
    Distance is never negative.
    With that in mind, which is the answer?
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  4. #4
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    Re: Equalities -Need Help

    Hmmm...so (b) is the answer?
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  5. #5
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    Re: Equalities -Need Help

    Wait....not (b) .... I think its (c). Pls correct me if im wrong ((:
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  6. #6
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    Re: Equalities -Need Help

    Quote Originally Posted by weijing85 View Post
    Wait....not (b) .... I think its (c). Pls correct me if im
    Let A=\{x:-4<x<4\}~\&~B=(-\infty,-9)\cup(9,\infty).

    What is the minimum distance between those two sets?
    The answer is not c).
    Thanks from weijing85
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