The first question (sub-topic, if time is tight, take this sub-topic and leave):

Make vertical auxiliary lines at point C and point B respectively, and decompose the quadrilateral into 1 trapezoid and 2 triangles. According to the known information, the total area can be obtained.

Then get the area of △OCD (half of the total area);

Find the length of OD according to the total area of △OCD (find the bottom length according to the area and height), that is, know the coordinates of point D.

The second question (although this is not difficult, it is relatively roundabout):

We first find the value of k according to the known conditions.

Let the two intersections of a straight line and a parallelogram be M(3/k, 2) and N (1/k, 0)-① I put the breakthrough on the n coordinate;

Because I can't remember whether there is a theorem or formula about ON=MB, it's easy to prove anyway. Let's set the coordinates of m and n first, and substitute them for calculation in one round.

Then we get the abscissa of on = MB = 4-3/k-② B minus the abscissa of M, so we get the coordinates of N points through another dimension.

According to ① and ②: 4-3/k =1/k; After calculation, k= 1, we can get this score, and then do it according to our actual situation.

Step 2, the upper/lower opening parabola has two intersections with the coordinate system (it must have one intersection with the Y axis, that is, it has only one intersection with the X axis).

That is to say, the fixed-point ordinate of parabola is 0, and the formula of vertex coordinate is forgotten. . . .

PS: If there are two intersections with the X-axis coordinate, you can continue the calculation attempt. I really forgot.

PS2: I can only guarantee to achieve the 1 step of the second question. The second step is up to you. It has been more than ten years. I really forgot.