Solution: -x+b=k/x to get the value of x (solved by formula). Substituting the abscissa of b into y=-x+b to get that the ordinate of b is equal to the abscissa of a, that is, MO=ON. Because the area of the triangle AMO is equal to the area of the triangle BON, and MA=BN, so: △ AOM △ BON. AB uses the distance formula between two points to calculate AB= root number 2 times the square of root number B minus 4K, because AB= root number 2, so the square of root number B minus 4K = 1, and on-bn = the square of root number B minus 4K, so ON-BN= 1. The most difficult thing is to solve the following third conclusion:

Over o makes OM perpendicular to AB at point d.

, it can be concluded that the area of triangle AOM and AOD is equal, and the area of triangle ODB and OBN is equal, so the area of triangle AOB is K.

Option d