Since point Q is on the inverse proportional function, m=2/3 times 4, so m=8/3, so: 8/3=-4+b, and b=20/3.

Therefore, y = (2x)/3 and y =-x+20/3.

(2) There are many methods, taking area subtraction as an example.

Idea: the area of OPQ is equal to the area of OAB minus the areas of OPB and OAQ.

Let x=0 get the ordinate of b from the linear equation, and y=0 get the abscissa of a;

Because the straight line intersects the inverse proportional function, the simultaneous equations can be equal to the coordinates of P, then the area of OPB is equal to the ordinate of B multiplied by the abscissa of P 1/2, the abscissa of OAQ multiplied by the ordinate of Q, that is, the value of M multiplied by 1/2, and then the area of OAB is equal to the ordinate of B multiplied by the abscissa of A multiplied by 1/2, and the answer can be obtained! I hope this helps.