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Math Help - Finding equation of parabola passing through three known points.

  1. #1
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    Finding equation of parabola passing through three known points.

    Find the equation of a parabola that passes through the points (-2,3), (-1,1) and (1,9). Any help would be great;so confused right now. Stuck on this for over a hour now!
    Last edited by mr fantastic; June 28th 2010 at 10:08 PM.
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  2. #2
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    Well the equation of a parabola is y = ax^2+bx+c

    substitute your points in one at a time then solve remaining system of equations.

    Here's a kicker.

    (-2,3): 3 = a(-2)^2+b(-2)+c \implies 3 = 4a-2b+c

    Now you have a go.
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  3. #3
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    okay ill try some more now. ty
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  4. #4
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    If you substitute the values into the general quadratic equation, then you get a linear system, which you can solve with substitution methodes.
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