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Math Help - Whats the domain?????

  1. #1
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    Exclamation Whats the domain?????

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  2. #2
    MHF Contributor arbolis's Avatar
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    The domain is all the x that make x(x-18)>0.
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  3. #3
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    Wink

    I know that..but i need the domain in interval notation of that function
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  4. #4
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by arbolis View Post
    The domain is all the x that make x(x-18)>0.
    Quote Originally Posted by sadieann View Post
    I know that..but i need the domain in interval notation of that function
    Well, if you know this is the case, then for what values of x is this inequality true? Just solve the inequality. Its fairly straightforward. Once you solve the inequality, the intervals become pretty obvious.

    --Chris
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  5. #5
    MHF Contributor arbolis's Avatar
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    Ok. Note that x(x-18) vanishes when x equals 0 or 18. Note also that y=x(x-18)=x^2-18x is an equation of a parabola with a global minimum. That mean that x(x-18)\geq 0 when x \in (-\infty,0] U [18,+\infty,), that's your domain.
    EDIT: I'm sorry in my first post, it should be "The domain is all the x that make x(x-18)\geq 0."
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  6. #6
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    Thank you so much man.
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  7. #7
    MHF Contributor arbolis's Avatar
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    A pleasure to help. I understand you were in a rush but when you have time, try to understand what I did and ask us if you don't understand. Good luck.
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