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Math Help - did i do this parabola question right?..

  1. #1
    Junior Member
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    Sep 2009
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    did i do this parabola question right?..

    i don't know if i did this right...

    sketch 2x^2 +12x -14 and indicate all its vertex and intercepts

    my vertex tht i got is (-3,-26)

    my y-intercept is (0,-14) x-intercept (-1,0) and (7,0)
    is this right?
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  2. #2
    Senior Member Stroodle's Avatar
    Joined
    Jun 2009
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    Hi there.

    One method of finding the minimum of the graph is to convert it to turning point form by completing the square:

    y=2x^2-12x-14

    y=2(x^2+6x-7)

    y=2((x+3)^2-16)

    y=2(x+3)^2-32

    You can now see that the minimum is at (-3,-32)

    Now to find the x-intercepts let y=0

    2(x+3)^2-32=0

    (x+3)^2-16=0

    (x+7)(x-1)=0

    Therefore the x-axis intercepts are at (-7,0) and (1,0)

    The y-intercept occurs where x=0 which is at (0,-14)

    You should post your working so we can see where you went wrong.
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