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Inequalities & Regions. OCR Module 8. An inequality?. An INEQUALITY shows a relationship between two variables, usually x & y Examples y > 2x + 1 y < x – 3 3x + 4y = 12. What are you required to do?. Read a graph and write down the inequalities that contain a region
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Inequalities & Regions OCR Module 8
An inequality? • An INEQUALITY shows a relationship between two variables, usually x & y • Examples • y > 2x + 1 • y < x – 3 • 3x + 4y = 12
What are you required to do? • Read a graph and write down the inequalities that contain a region • Draw inequalities and indicate the region they describe • You need to know how to plot straight line graphs [covered in Stage 7]
y x For example X=2 x > 2 When dealing with ONE inequality, we SHADE IN the REQUIRED REGION
y x For example X=-2 x < -2
y x For example y < -1 y=-1
y (1,2) x For example y= 2x+1 y < 2x +1 Which side is shaded? Pick a point NOT on line Is 2 < 2 x 1 + 1 ? YES (1,2) lies in the required region
y (2,1) x For example y= 3x-2 y > 3x - 2 Which side is shaded? Pick a point NOT on line Is 1 > 3 x 2 - 2 ? NO (2,1) does NOT lie in the required region
Drawing Inequalities Back to Stage 7
y (2,1) x How to draw graph of equation y = 3x + 2 Shade IN the Region for y > 3x + 2 Is 1 > 3 x 2 + 2 ? NO (2,1) does NOT lie in the required region
y (3,2) x How to draw graph of equation 4y + 3x = 12 Shade IN the Region for 4y + 3x > 12 Is 4 x 2 + 3 x 3 > 12 ? YES (3,2) DOES lie in the required region
Exam Question An example
(3,2) 2 < 3 ? y < 3 x + y = 4 x = 4 3 < 4 ? y = 3 x < 4 3 + 2 > 4 ? x + y > 4