MathChapter 4: Linear Inequalities and Graphs
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Prompt
What is a system of inequalities?
💡Every constraint applies.
Answer
Two or more inequalities involving the same variables.
ExampleA feasible point must satisfy the complete set.
Prompt
What represents a system's solution set?
Answer
The intersection of all individual solution regions.
ExampleKeep only the shared overlap.
Prompt
How do you test a candidate point?
💡One failure rejects it.
Answer
Substitute it into every inequality; every statement must be true.
ExampleMake a true/false checklist.
Prompt
Does satisfying one inequality make a point a system solution?
💡A system is not OR.
Answer
No. It must satisfy all inequalities.
ExampleA point outside one half-plane is rejected.
Prompt
What does an empty overlap mean?
💡The constraints are incompatible.
Answer
The system has no solution.
Example\(y>4\) and \(y<1\) cannot both hold.
Prompt
How are mixed boundary styles handled?
💡Do not give every line one style.
Answer
Choose solid or dashed separately from each inequality's operator.
ExampleOne system may contain both styles.
Prompt
Can a dashed boundary segment belong to the solution?
💡Even if other constraints allow it.
Answer
No, because its strict inequality excludes equality.
ExamplePoints on \(y<x\)'s boundary are excluded.
Prompt
Can a solid boundary segment belong to the solution?
💡Inclusion is necessary, not sufficient.
Answer
Yes, but only where it also satisfies every other inequality.
ExamplePart of a solid line may lie outside another half-plane.
Prompt
What is the reliable system graphing order?
💡Repeat before combining.
Answer
Graph and shade each inequality, then identify their common intersection.
ExampleVerify a point from the overlap.
Prompt
How do labeled-region questions work?
💡Do not rely only on visual darkness.
Answer
Test a representative point from each candidate region in every inequality.
ExampleChoose points away from boundaries.
Prompt
How can sign constraints identify a quadrant?
💡Quadrant IV has positive x and negative y.
Answer
Combine x and y restrictions with quadrant sign patterns.
Example\(x>0\) and \(y<0\) force Quadrant IV.
Prompt
What is the difference between union and intersection shading?
💡Systems use AND by default.
Answer
Union accepts at least one condition; a system requires the intersection satisfying all conditions.
ExampleDo not keep every pastel area.
Prompt
What does a vertical system boundary control?
💡Its equation is \(x=a\).
Answer
A restriction on x and therefore left/right position.
Example\(x\ge2\) shades right of a solid vertical line.
Prompt
What does a horizontal system boundary control?
💡Its equation is \(y=b\).
Answer
A restriction on y and therefore below/above position.
Example\(y<4\) shades below a dashed horizontal line.
Prompt
Why verify a graph intersection algebraically?
💡Use a simple interior point.
Answer
Visual overlap can be misread near boundaries, while substitution checks every constraint exactly.
ExampleDo not infer inclusion from color alone.
Prompt
Can a system contain three or more inequalities?
💡Each new constraint may shrink the region.
Answer
Yes. Continue intersecting until every constraint has been applied.
ExampleA feasible polygon can have several boundary edges.
Prompt
How do contextual systems arise?
💡All real-world constraints apply together.
Answer
Each resource, minimum, maximum, or relationship becomes a separate inequality.
ExampleAlso include nonnegative counts when stated or inherently required.
Prompt
What is a common overlap-shading error?
💡Darker is not automatically correct.
Answer
Highlighting the union of individual regions instead of their shared intersection.
ExampleTest a point in the proposed final region.
Prompt
What if two parallel inequalities point away from each other?
💡Compare the required ranges.
Answer
Their intersection may be empty.
Example\(y>5\) and \(y<2\) has no solution.
Prompt
What is the fastest SAT check for a proposed system solution?
💡Direct testing avoids redrawing.
Answer
Substitute the ordered pair into each inequality and stop at the first false statement.
ExampleIf all are true, the point is in the intersection.
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