This topic examines the synthesis of quadratic function, involving parabolic symmetry axis, properties of rectangle, parabolic analytical formula of undetermined coefficient method, linear analytical formula of undetermined coefficient method, Pythagorean theorem, triangle area, maximum value of quadratic function, application of classification thought and other knowledge points.

The first question can get the point coordinates according to the symmetry axis of parabola and the properties of rectangle, and the analytical formula of parabola can be obtained according to the undetermined coefficient method.

Solution: (1) Because the symmetry axis of parabola is x= 1, the three vertices of rectangular OCDE are C (3,0), D (3,4) and E (0,4) respectively. Detailed answers/exercises/math /7994 1 Look here.

In the plane rectangular coordinate system, the three vertices of the rectangular OCDE are C (3 3,0), D (3 3,4) and E (0 0,4) respectively. Point A is on DE, the parabola with vertex A passes through point C, and the axis of symmetry x= 1 intersects the X axis at point B, connecting EC and AC. Points p and q are moving points.

(1) Fill in the blank: the coordinate of point A is-; The analytical formula of parabola is-

(2) In Figure ①, if point P moves from point O to point C at a speed of 1 unit/sec on the OC line, point Q moves from point C to point E at a speed of 2 units/sec on the CE line, and when one point reaches the end point, the other point stops moving. When t is what value, is △PCQ a right triangle?