1. An ordered pair (a, b) is a ________ of an inequality in x and y when the inequality is true after a and b are substituted for x and y, respectively.
2. The ________ of an inequality is the collection of all solutions of the inequality.
3. A ________ of a system of inequalities in x and y is a point (x, y) that satisfies each inequality in the system.
4. The ________ ________ of a system of inequalities in two variables is represented by the region that is common to every graph in the system.