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Math Help - Equations and range of values..

  1. #1
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    Cool Equations and range of values..

    Hi, thnx for help

    How do i find the range of values of k for which the equation x^2+5x+k=0 (i dont know how to find values )

    and also how to solve the equation 4x^2+20x+25=0 i tried to use the formula but i didnt get a answer that worked... thnx
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Chez_ View Post
    Hi, thnx for help

    How do i find the range of values of k for which the equation x^2+5x+k=0 (i dont know how to find values )
    use the quadratic formula.

    If x^2 + 5x + k = 0, we must have:

    x = \frac {-5 \pm \sqrt{25 - 4k}}2

    this of course, only has real solutions when we are withing the domain of the square root. thus we require 25 - 4k \ge 0. what is the range of k-values for which this happens?

    and also how to solve the equation 4x^2+20x+25=0 i tried to use the formula but i didnt get a answer that worked... thnx
    the quadratic formula can work, but it is overkill. this equation can be factored.

    4x^2 + 20x + 25 = (2x + 5)(2x + 5) = (2x + 5)^2

    So, 4x^2 + 20x + 25 = 0 \implies (2x + 5)^2 = 0.

    now continue
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