According to the equation, we can get the active region where △ABC of the black region is the point (x, y). The straight line A is X+Y=m, and only when the point (x, y) is at point A, Z=X-Y is obviously the smallest? At this time, the straight line z is X-Y=- 1? The point A of the solvable equation is (2,3), and m=5 is brought into the third equation.

2.

Take the upper part of the graph, that is, the above graph, with m and n as the midpoint, and its edge graph is equivalent to △OMN in the graph, with an area of √3/4, then MN=ON= 1, then CD= 1? So the area of △OCD is 1/2, so the surface area is 1/2×8=4.