Mathematics
Grade 9
15 min
Is (x, y) a solution to the system of inequalities?
Is (x, y) a solution to the system of inequalities?
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Introduction & Learning Objectives
Learning Objectives
Define a system of linear inequalities and its solution.
Substitute the coordinates of an ordered pair (x, y) into a linear inequality.
Evaluate whether a substituted inequality results in a true or false statement.
Systematically test an ordered pair against all inequalities in a given system.
Determine if an ordered pair is a solution to a system of inequalities based on the test results.
Explain why an ordered pair is or is not a solution to a system.
Ever tried to pick a movie that is under 2 hours long AND has a rating of over 80%? 🎬 You're already checking for solutions to a system of inequalities!
In this tutorial, you will learn a straightforward method to check if a specific point (x, y) is a valid solution to a system of linear inequaliti...
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Key Concepts & Vocabulary
TermDefinitionExample
Linear InequalityA mathematical statement that compares two expressions using an inequality symbol (<, >, ≤, ≥), where at least one expression is linear. It describes a region on the coordinate plane.y < 2x + 3
System of Linear InequalitiesA set of two or more linear inequalities that are considered together. A solution must work for all of them simultaneously.{ y ≥ x - 4, y < -x + 5 }
Ordered PairA pair of numbers, written as (x, y), that represents a specific point on a coordinate plane.(4, 1)
Solution to an InequalityAn ordered pair (x, y) that makes the inequality a true statement when its values are substituted for the variables.For y > x, the point (3, 5) is a solution because substituting gives 5 > 3, which is true.
Solution to a System of In...
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Core Formulas
The Substitution Principle
For a given point (x_0, y_0) and an inequality like y < mx + b, substitute x_0 for x and y_0 for y to check if the statement y_0 < mx_0 + b is true.
This is the fundamental action for testing a point. You replace the variables with the given numbers to see if the inequality holds true.
The All-or-Nothing Rule
A point (x_0, y_0) is a solution to a system {I_1, I_2, ..., I_n} if and only if (x_0, y_0) satisfies I_1 AND I_2 AND ... AND I_n.
This is the master rule for systems. A point must satisfy every single inequality without exception. If even one test results in a false statement, the point is not a solution to the system.
4 more steps in this tutorial
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Challenging
If the point (a, a+2) is a solution to the system { y > 2x, x > 0 }, what must be true about 'a'?
A.a < 2
B.a = 2
C.a < -2
D.a > 2
Challenging
The point (2, 5) is NOT a solution to the system { y < 3x, y > 4 }. If you could change exactly one inequality symbol to make (2, 5) a solution, which change would work?
A.Change y < 3x to y ≤ 3x in the first inequality.
B.Change y > 4 to y ≥ 4 in the second inequality.
C.Change y < 3x to y > 3x in the first inequality.
D.Change y > 4 to y < 4 in the second inequality.
Challenging
Is the origin, (0, 0), a solution to the system { y ≤ x, y > -2x }?
A.Yes, because 0 = 0 and 0 > 0.
B.No, because while 0 ≤ 0 is true, 0 > 0 is false.
C.No, because 0 ≤ 0 is false.
D.Yes, because the origin is always a solution.
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