General form of Parabola with Axis parallel to y axis: (x-a)2 = 4k(y-b)
From (0,0), we have a2 = -4kb ---------------------------- A
From (1,0), we have 1+a2-2a = -4kb ------------------------------ B
From (-2,4), we have 4+a2+4a = 16k - 4kb -------------------------------- C
From A and B, 1-2a = 0, so a = 1/2.
From C and A, 4+4a=16k or 1+a=4k or k=1/4 + a/4 = 3/8. so k = 3/8.
From A, 1/4 = -3b/2 or b = -1/6.
So equation of the parabola is (x - 1/2)2 = 4 * (3/8) * (y + 1/6).
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