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Math Help - discriminant

  1. #1
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    discriminant

    I know this sounds stupid but I actually need help with this!

    in x + x + 3

    why is the discriminant always positive?
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by me2612 View Post
    I know this sounds stupid but I actually need help with this!

    in x + x + 3

    why is the discriminant always positive?
    who told you the discriminant was positive? it is negative here. this quadratic has no real roots
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  3. #3
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    Quote Originally Posted by me2612 View Post
    I know this sounds stupid but I actually need help with this!

    in x + x + 3

    why is the discriminant always positive?
    the discriminant is never positive since b^2-4ac is the formula for the discriminant you would get -11 which would mean that equation only has imaginary roots.
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  4. #4
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    That's why I'm stuck, the question paper definitely says its always positive
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  5. #5
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by me2612 View Post
    That's why I'm stuck, the question paper definitely says its always positive
    are you sure it is not something like x^2 + x - 3? or -x^2 + x + 3 otherwise, it's a typo
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  6. #6
    MHF Contributor red_dog's Avatar
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    The discriminant is negative, so the function f(x)=x^2+x+3 is always positive.
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  7. #7
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    Quote Originally Posted by red_dog View Post
    The discriminant is negative, so the function f(x)=x^2+x+3 is always positive.
    Here's a short proof

    x^2 + x + 3 = \frac{{\left( {x + 1} \right)^2 + x^2 + 5}}<br />
{2}

    The conclusion follows.
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