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    2008 15th of May C1 paper

    10) ii) The curve C has equation y = 3x^2 - 4x + 7. The line L has the equation
    y = 2x + k, where k is a constant. Given that L and C do not intersect, find the range of possible values of k.

    Any help?

    Will rep.

    Thanks.
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    Equate the curve and line, rearrange to form a quadratic equation.
    Since they don't intersect, what does that tell you about the solutions of the quadratic and it's discriminant...?
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    3x^2 -6x + (7-k) = 0
    Discriminant = 36 - 4x3x(7-k)
    36 - 4x3x(7-k) < 0
    36 < 84 - 12k
    - 48 < -12 k
    12k < 48
    k < 4
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    First make the equation of the line equal to the quadratic, so 3x^2-4x+7=2x+k.
    Then rewrite as 3x^2-6x+7-k=0

    The discriminant is (36-12(7-k)) and for no solutions, the discriminant must be negative, so

    36<12(7-k)
    3<7-k
    k<4
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    Wtf why have I been thumbed down?
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    (Original post by joe3469)
    Wtf why have I been thumbed down?
    There's no reason why you should have been, your maths is right :confused:
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    (Original post by jameswhughes)
    There's no reason why you should have been, your maths is right :confused:
    Lol oh well
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    (Original post by jameswhughes)
    There's no reason why you should have been, your maths is right :confused:
    I second this.
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    (Original post by Tempa)
    2008 15th of May C1 paper

    10) ii) The curve C has equation y = 3x^2 - 4x + 7. The line L has the equation
    y = 2x + k, where k is a constant. Given that L and C do not intersect, find the range of possible values of k.

    Any help?

    Will rep.

    Thanks.
    Here you go, just have the mark scheme

    Enjoy
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