本文试图说明:二元一次不等式组的解在直角坐标系中所表示的封闭区域,对于不等式或极值的有关题解有特殊的作用。1 封闭区域存在的依据我们知道:在直角坐标系中,点P(x_1,y_1)在直线Ax+By+C=0上时,Ax_1+By_1+C=0;点P(x_1,y_1)不在该直线上时,有Ax_1+By_1+C>0或Ax_1+By_1+C<0,这样直线Ax+By+C=0把坐标平面划分为两部分区域,使Ax+By+C>0的点P(x_1,y_1)所在区域称为Ax+By+ This paper attempts to show that the solution of the solution of the binary inequalities in the Cartesian coordinate system has a special effect on the solution of inequality or extreme values. 1 The basis for the existence of a closed region We know that in a Cartesian coordinate system, point P(x_1,y_1) is on the line Ax+By+C=0, Ax_1+By_1+C=0; point P(x_1,y_1) is not On this straight line, there are points Ax_1+By_1+C>0 or Ax_1+By_1+C<0, so that the straight line Ax+By+C=0 divides the coordinate plane into two parts, so that Ax+By+C>0 points The area where P(x_1,y_1) is located is called Ax+By+