http://community.9cbs.net/expert/topic/3756/3756475.xml?temp =.3623011 The coordinates (x1, y1) of the 2 points on the parabola (X2, Y2) (and 2 points are Two tests of the vertex of the parabola), as well as the ordinate K, and the parabolic opening facing up, ie A> 0.
The general formula of the parabolic: y = a * x ^ 2 b * x C is the value of the A, B, C, and the abscissa hth coordinates H of the vertex.
This problem can solve the form of the assumption equation is y = a (xb) ^ 2 kΩ to ensure that the minimum number of Y1-K = A (x1-b) ^ 2 y2-k when the minimum number of y1-k = a (x1-b) ^ 2 y2-k when the minimum of K, X = B = a (x2-b} ^ 2 According to the hormone hypothesis, it is obvious that Y1 and Y2 are greater than K, otherwise it is impossible to have answers that this means SQRT ((Y1-K) / (Y2-K)) inevitably effective After the data is opened, the division is removed, obtaining two equations SQRT ((Y1-K) / (Y2-K)) = X1-B / X2-B SQRT ((Y1-K) / (Y2-K)) = - (X1-B / X2-B) Only the latter is effective, because the correct answer B is located between X1 and X2, then can solve B, then bring back to solvent A and then Y = A (XB) ^ 2 K Expands become Y = AX ^ 2 BX C mode, thus gaining the value of A, B, and C, complete calculation is
M = SQRT ((Y1-K) / (Y2-k)) b = (x1 x2 * m) / (m 1) a = (Y1-K) / ((x1-b) * (x1-b ))
A = a; b = 2 * a * bc = k b * B vertex coordinate (B, K) parabola equation Y = a * x ^ 2 b * x c
