Linear Inequalities in Two Variables
Tell whether each statement is true or false when x = -2 and y = 1: ◦ 2x – y < 5 TRUE ◦ x + 3y > 0 TRUE
New vocabulary: Linear inequality in two variables Half-plane
Can be written in one of these forms where A, B, and C are constants: ◦ Ax + By < C ◦ Ax + By > C An ordered pair (x, y) is a solution of a linear inequality if the inequality is true when the values of x and y are substituted into the inequality.
Check whether the given ordered pair is a solution of 2x + y < 5 a. (1,4)b. (2, -1)
Check whether the given ordered pair is a solution of x – 3y > 4 a. (0, 0)b. (4, -1)c. (-2, -2)
The graph of a linear inequality in two variables is the graph of all solutions of the inequality. The boundary line of the inequality divides the coordinate plane into two half-planes. Shaded half-plane: points that are solutions Non-shaded half-plane: contains the points that are not solutions
A dashed line indicates that the points on the line are NOT solutions. ( >, < ) A solid line indicates that the points on the line ARE solutions. ( >, < )
x > -1 y > 1 y < -3 x < 4
Graph y < 2x in a coordinate plane Graph 3x – 2y > 8 in a coordinate plane
Graph the inequality in a coordinate plane: a. y > xb. y < -3xc. x + 2y < 6
p. 182 – even, 32-34, even, 44-46