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Math Help - Please help- discriminants?

  1. #1
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    Please help- discriminants?

    Show that it is impossible to find two real numbers with a product of 5 and a sum of 4.

    Hint: think discriminants.
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  2. #2
    Bar0n janvdl's Avatar
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    Quote Originally Posted by greghunter View Post
    Show that it is impossible to find two real numbers with a product of 5 and a sum of 4.

    Hint: think discriminants.
    xy = 5
    x + y = 4

    xy = 5 \rightarrow y = \frac{5}{x}

    x + \frac{5}{x} = 4 AND x \neq 0

    x^2 - 4x + 5 = 0

    Now find delta.

    b^2 - 4ac = 16 - 4(1)(5) = -4

    Therefore there exists only a complex solution.
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