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Math Help - finding the domain of the function

  1. #1
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    Mar 2008
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    Exclamation finding the domain of the function

    can someone please explain to me how to do this.

    Find the value of a which will ensure that the domain of the function
    f(x) = −9
    √(a x+10) (-9 over sqrt(ax+10))
    is the interval (−∞, 3), i.e. x < 3.

    do you need to find the value of a, when x is 3? I'm a bit confused :S
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  2. #2
    Senior Member Sambit's Avatar
    Joined
    Oct 2010
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    The domain is x<3 which gives ax+10<3a+10

    The function will be defined only if ax+10>0 (since square root of a negative term is not possible)

    => 3a+10>0

    => a>-\frac{10}{3}
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