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Math Help - Complex number equation

  1. #1
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    Complex number equation

    I need to determine what I can say about "c" if:

    If c is a real number and you know that the equation
    z^2 + 2z + c = 0 has at least one solution that is not real, what can you say about c?

    I do not know that I have information to say anything about c, other than the fact that it is real as is stated. But, I know that z can not equal 0. Since we know it is the complex portion of this equation I guess that that is obvious. Are we able to conclude if c is greater than 1 or less than or equal to 1??? If so, please explain. Thank you! Frostking
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  2. #2
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    Quote Originally Posted by Frostking View Post
    I need to determine what I can say about "c" if:

    If c is a real number and you know that the equation
    z^2 + 2z + c = 0 has at least one solution that is not real, what can you say about c?

    I do not know that I have information to say anything about c, other than the fact that it is real as is stated. But, I know that z can not equal 0. Since we know it is the complex portion of this equation I guess that that is obvious. Are we able to conclude if c is greater than 1 or less than or equal to 1??? If so, please explain. Thank you! Frostking
    For a quadratic equation to have a non-real solution, the discriminant must be less than zero. Therefore ....
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