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Math Help - Inequality

  1. #1
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    Inequality

    I have an inequality and I don't know if I need to use the quadratic formula or not...it's like this:

    x^2 + 8x - 4 < 0

    Can't be factored with decomposition so yeahhhh, any suggestions?
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  2. #2
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    Quote Originally Posted by cjh824 View Post
    x^2 + 8x - 4 < 0
    Can't be factored with decomposition so
    With real roots it can always be factored.
    x^2  + 8x - 4 = \left[ {x - \left( {\frac{{ - 8 + \sqrt {80} }}<br />
{2}} \right)} \right]\left[ {x - \left( {\frac{{ - 8 - \sqrt {80} }}<br />
{2}} \right)} \right]
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  3. #3
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    x^{2}+8x-4<0\implies (x+4)^{2}<20\implies -2\sqrt{5}-4<x<2\sqrt{5}-4.
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