∫tan∠OCA = OA/OC = 1/3，
∴OA= 1，
∴ The coordinate of point A is (1, 0).
∫S△ABC =？ ×AB×OC=6。
∴? ×AB×3=6
AB=4，
∴ The coordinates of point B are (-3,0) or (5,0).
(2) When the coordinate of point B is (-3,0), because the parabola passes through A( 1 0) and c (0,3),
Can the analytical formula be y=-x? -2x+3, and the vertex coordinate is (1, 4).
When the coordinate of point B is (5,0), because the parabola passes through point A (1, 0) and point C (0,3),
The analytical formula is y=(3/5)x? -( 18/5)x+3, and the vertex coordinate is (3,-12/5).