Then the coordinates of point b are (a/k, k/a).

The coordinate of point A is (a, 1/a).

The area is 1/2 because both a and b are on y =1/x. The first one is right.

The area of pdoc is calculated by the coordinates of point P, so the area of pboa is still k- 1. The second one is right.

Pa = k/a-1/a = (k-1)/a Pb = a-a/k = (k-1) * a/k, so the third one is wrong.

When a is the midpoint of pc, then k/a=2* 1/a k=2.

It can be concluded that the abscissa of point B is a/2, which is exactly half of the abscissa of point P, so the fourth one is right.