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Math Help - help with a quadratic equation question

  1. #1
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    help with a quadratic equation question

    One of the roots of the equation x2 + kx -6 = 0 is 3, and k is constant. Which is greater: k or -1

    Now if you plug in 3 for x you get -1 which makes sense, but when I first did the problem I tried to solve it by factoring the equation and I came up with k= -1 or 1 as shown below.

    (x + 3)(x - 2) = x2 + x - 6 here k = 1
    (x - 3)(x + 2) = x2 - x - 6 here k = -1

    where am I going wrong? thank you for the help
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  2. #2
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    Re: help with a quadratic equation question

    Hello, buckethdd!

    One of the roots of the equation x2 + kx -6 = 0 is 3, and k is constant.
    Which is greater: k or -1 ?

    Now if you plug in 3 for x, you get -1, which makes sense,
    but when I first did the problem I tried to solve it by factoring the equation
    and I came up with k= -1 or 1 as shown below.

    (x + 3)(x - 2) = x2 + x - 6 here k = 1 . The roots are -3 and 2.

    (x - 3)(x + 2) = x2 - x - 6 here k = -1

    Where am I going wrong? thank you for the help.
    Follow Math Help Forum on Facebook and Google+

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