Linear programming problems involve maximizing or minimizing a linear objective function subject to linear inequality constraints. These problems can be analyzed geometrically for problems with two variables. The solution set of a linear equation in two variables forms a straight line, while a linear inequality forms either the half-plane on one side of the line or the other, depending on whether a test point satisfies the inequality. To graph a linear inequality, one first graphs the corresponding equality and then tests a point to determine which half-plane is the solution set.