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Math Help - Quadratic Functions exam paper question

  1. #1
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    Quadratic Functions exam paper question

    Given that the equation

    kx^2 - 4x + k - 3 = 0

    has equal roots, find the value of "k".

    I know that a=k, b=-4, and c=k-3.

    Then to put it into b^2 - 4ac I'd get:

    (-4)^2 - 4 (k) (k-3) = 0
    16 - 4k^2 + 12k = 0
    [I can cancel down to:] 4 - k^2 + 3k = 0

    But I'm not sure what to do from here can someone please help
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  2. #2
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    Quote Originally Posted by db5vry View Post
    Given that the equation

    kx^2 - 4x + k - 3 = 0

    has equal roots, find the value of "k".

    I know that a=k, b=-4, and c=k-3.

    Then to put it into b^2 - 4ac I'd get:

    (-4)^2 - 4 (k) (k-3) = 0
    16 - 4k^2 + 12k = 0
    [I can cancel down to:] 4 - k^2 + 3k = 0

    But I'm not sure what to do from here can someone please help
    Now you have to solve 4 - k^2 + 3k = 0 => k^2 - 3k - 4 = 0.
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  3. #3
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    keep going, solve last equation: k^2-3k-4=0 (k-4)(k+1)=0, k=4;-1
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