Y=-2/3x+z/3, that is, a set of straight lines with a slope of -2/3 in rectangular coordinate system?

You should draw a triangle area according to the constraints, so that the maximum and minimum values of Z are obtained at three vertices. Find out that the three vertices are (1, 1) (1, 5) (4,2), because z is 5? , 17, 14, that is, the maximum value of z is 17? The minimum value is 5

In fact, we can also directly see which vertex is the largest according to the slope.