7.4 GRAPHING LINEAR INEQUALITIES IN TWO （7.4图形线性不等式两种）.pdf

390 (7-22) Chapter 7 Systems of Linear Equations and Inequalities G R A P H I N G L I N E A R I N E Q U A L I T I E S 7.4 I N T W O V A R I A B L E S I n t h i s You studied linear equations and inequalities in one variable in Chapter 2. In this section we extend the ideas of linear equations in two variables to study linear s e c t i o n inequalities in two variables. Definition Definition Graph of a Linear Inequality Linear inequalities in two variables have the same form as linear equations in two Using a Test Point to Graph variables. An inequality symbol is used in place of the equal sign. an Inequality Applications Linear Inequality in Two Variables If A , B, and C are real numbers with A and B not both zero, then Ax By C is called a linear inequality in two variables. In place of , we can also use , , or . The inequalities 3x 4y 8, y 2x 3, and x y 9 0 are linear inequalities. Not all of these are in the form of the definition, but they could all be rewritten in that form. An ordered pair is a sol