Mathematics Grade 9 15 min

Does (x, y) satisfy the inequality?

Does (x, y) satisfy the inequality?

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Introduction & Learning Objectives

Learning Objectives Define what it means for an ordered pair to be a solution to a linear inequality. Substitute the x and y values from an ordered pair into a given linear inequality. Evaluate the resulting numerical statement to determine if it is true or false. Confidently conclude whether a given ordered pair satisfies an inequality. Differentiate between strict inequalities (<, >) and non-strict inequalities (≤, ≥) when testing points. Explain that a solution to a linear inequality is any point within the shaded region of its graph. Planning a party and have a budget? Let's say you can spend *at most* $50 on pizza and soda. How do you check if buying 3 pizzas and 5 sodas works? 🤔 This tutorial will teach you a straightforward algebraic method to check if an...
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Key Concepts & Vocabulary

TermDefinitionExample Linear InequalityA mathematical statement that compares two linear expressions using an inequality symbol (<, >, ≤, or ≥). It describes a region on the coordinate plane.y > 2x - 1 Ordered Pair (x, y)A pair of numbers, written in the form (x, y), that represents a specific location on a coordinate plane.(4, 5), where x=4 and y=5. SolutionAn ordered pair that makes the inequality a true statement when its values are substituted for x and y.For the inequality y < x, the point (3, 1) is a solution because 1 < 3 is a true statement. To SatisfyAn ordered pair 'satisfies' an inequality if it is a solution. This means it makes the inequality true.The point (5, 10) satisfies the inequality y ≥ 2x because substituting gives 10 ≥ 2(5), which simplifies...
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Core Formulas

The Substitution Method Given an inequality and a point (x₀, y₀), substitute x₀ for every 'x' and y₀ for every 'y' in the inequality. This is the first and most critical step. It transforms the algebraic inequality into a numerical statement that can be tested for truth. The Truth Test After substituting, simplify both sides of the inequality. If the resulting statement is mathematically true, the point is a solution. If it is false, the point is not a solution. This is the final check. A true statement like 5 > 2 means the point works. A false statement like 10 < 7 means the point does not.

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Sample Practice Questions

Challenging
A student tests if (2, 6) satisfies y ≤ 3x. They find that 6 ≤ 3(2) becomes 6 ≤ 6. They conclude it's not a solution because 6 is not 'less than' 6. Why is their conclusion incorrect?
A.Their initial substitution was wrong.
B.Their multiplication was wrong.
C.They ignored the 'or equal to' part of the ≤ symbol.
D.They should have flipped the inequality sign.
Challenging
A student is asked if (-4, 1) satisfies 2x - y < -9. Their work is shown: Step 1: 2(-4) - 1 < -9 Step 2: -8 - 1 < -9 Step 3: -9 < -9 Conclusion: The point is a solution. Where is the error?
A.The error is in Step 1 (incorrect substitution).
B.The error is in Step 2 (incorrect arithmetic).
C.The error is in Step 3 (incorrect simplification).
D.The error is in the Conclusion (misinterpreting the result of Step 3).
Challenging
For what value of 'k' will the point (k, 5) lie on the boundary line of the inequality 3x + 2y ≥ 16?
A.k = 3
B.k = 2
C.k = 6
D.k = 1

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