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Math Help - Considering the inequality

  1. #1
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    Considering the inequality

    Its been awhile seen I ask a question, but I need help with this inequality question.

    Consider the inequality: x^2 > -2x+15

    The solution of this inequality consists of one or more of the following intervals: (- Infinity,A), (A.B), and (B, Infinity) where A<B

    Find A:_____

    Find B:_____

    How do I solve this question? It's been awhile seen I tired to solve inequalty question. Can someone give me a crash course to solve this?
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  2. #2
    MHF Contributor Quick's Avatar
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    Quote Originally Posted by killasnake View Post
    Its been awhile seen I ask a question, but I need help with this inequality question.

    Consider the inequality: x^2 > -2x+15

    The solution of this inequality consists of one or more of the following intervals: (- Infinity,A), (A.B), and (B, Infinity) where A<B

    Find A:_____

    Find B:_____

    How do I solve this question? It's been awhile seen I tired to solve inequalty question. Can someone give me a crash course to solve this?
    x^2>-2x+15

    therefore: x^2+2x>15

    thus: x^2+2x+1>16

    then: (x+1)^2>16

    thus: x+1<-4 or x+1>4

    then: x<-5 or x>3

    which can be rewritten as -infinity<x<-5 or 3<x<infinity
    therefore you use intervals (-infinity,A) and (infinity,B) but not interval (A,B)
    Last edited by Quick; September 12th 2006 at 04:43 PM.
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  3. #3
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    oh duh! I remember now. Thank you for explaining that!
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