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Equation of Parabola Help?

Trying to make sense of the problems in my book but there's no real easy to follow examples.

Trying to solve this problem now:

Find the equation of the parabolas satisfying the given conditions. The vertex of each is at the origin.

Passes through (3, 3) and (12, 6).

The answer in the back is y^2= 3x

1 Answer

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  • 8 years ago
    Favorite Answer

    the vertex form of a parabola is y=a(x-h)^2+k where the vertex is (h,k)

    substitution (0,0) you get:

    y=ax^2

    now plug in you x and y coordinates from your two points to find "a"

    (NOTE: "a" must be identical for both points for the equation to be true)

    3=9a

    a=1/3

    6=144a

    a=1/24

    these dont match so you instead of having a squared x term you may have a squared y term so start all over and substitute y for x

    x=a(y-h)^2+k

    x=ay^2

    3=9a

    a=1/3

    12=a36

    a=1/3

    they are identical so that is "a" in the equation

    x=(1/3)y^2

    multiply by 3

    3x=y^2

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