How to calculate the vertex of a parabola given three points

Thanks David, I converted your pseudocode to the following C# code:

public static void CalcParabolaVertex(int x1, int y1, int x2, int y2, int x3, int y3, out double xv, out double yv)
{
    double denom = (x1 - x2) * (x1 - x3) * (x2 - x3);
    double A     = (x3 * (y2 - y1) + x2 * (y1 - y3) + x1 * (y3 - y2)) / denom;
    double B     = (x3*x3 * (y1 - y2) + x2*x2 * (y3 - y1) + x1*x1 * (y2 - y3)) / denom;
    double C     = (x2 * x3 * (x2 - x3) * y1 + x3 * x1 * (x3 - x1) * y2 + x1 * x2 * (x1 - x2) * y3) / denom;

    xv = -B / (2*A);
    yv = C - B*B / (4*A);
}

This is what I wanted. A simple calculation of the parabola’s vertex. I’ll handle integer overflow later.

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