AB:x=2

Composition equation:

y=2x

y=k/x

Solution: x=√(2k)/2, y=√(2k), c coordinate: [√(2k)/2, √(2k)]

Cd =-1/2 (∵ slope of CD ⊥ ob)

CD:[y-√(2k)]/[x-√(2k)/2]=- 1/2，y=-x/2+5√(2k)/4

Intersection of CD and AB: x=2, y=- 1+5√(2k)/4.

The function y = intersection of k/x and AB: x=2, y=k/2.

Since (the intersection of CD and AB) and (the intersection of function y=k/x and AB) are the same point, therefore:

- 1+5√(2k)/4=k/2

Solution: k 1=8 (irrelevant), k2= 1/2.

∴k= 1/2