MathChapter 4: Linear Inequalities and Graphs
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Prompt
What does \(x<a\) mean?
💡Equality is excluded.
Answer
Every value strictly less than \(a\).
ExampleUse an open endpoint at \(a\) and shade left.
Prompt
What does ‘at most \(a\)’ mean?
💡The boundary is allowed.
Answer
\(x\le a\).
ExampleAt most \(12\) means \(x\le12\).
Prompt
What does ‘at least \(a\)’ mean?
Answer
\(x\ge a\).
ExampleAt least \(5\) means \(x\ge5\).
Prompt
Which operators use an open number-line endpoint?
💡Strict inequalities exclude equality.
Answer
\(<\) and \(>\).
Example\(x>2\) is open at \(2\).
Prompt
Which operators use a closed number-line endpoint?
💡Equality is included.
Answer
\(\le\) and \(\ge\).
Example\(x\le4\) is closed at \(4\).
Prompt
When must an inequality sign reverse?
💡It is an order reflection.
Answer
When both sides are multiplied or divided by a negative number.
ExampleFrom \(-2x<8\), obtain \(x>-4\).
Prompt
Why does multiplying by a negative reverse order?
💡Compare \(2<5\).
Answer
It reflects values across zero, reversing their left-to-right order.
ExampleAfter multiplying by \(-1\), \(-2>-5\).
Prompt
Does adding a negative number reverse an inequality?
💡Only multiplication or division can trigger reversal.
Answer
No. Addition and subtraction preserve direction.
ExampleFrom \(x+(-3)<7\), add \(3\) without reversing.
Prompt
How do you solve a multi-step inequality?
💡Use equation-like steps.
Answer
Simplify, collect variables, collect constants, then isolate while monitoring the final divisor's sign.
ExampleReverse only if the isolating division is negative.
Prompt
What is the transitive inequality property?
💡It chains order.
Answer
If \(a<b\) and \(b<c\), then \(a<c\).
ExampleIf \(p<4\) and \(4<9\), then \(p<9\).
Prompt
Translate ‘does not exceed \(k\).’
💡Exceed means go above.
Answer
The quantity is \(\le k\).
ExampleA load that does not exceed \(60\) satisfies \(w\le60\).
Prompt
Translate ‘no less than \(k\).’
💡It cannot be below the boundary.
Answer
The quantity is \(\ge k\).
ExampleNo less than \(20\) means \(n\ge20\).
Prompt
How is an inequality solution different from an equation solution?
💡Think solution set.
Answer
It usually describes an interval or ray of values, not one isolated value.
Example\(x>3\) has infinitely many real solutions.
Prompt
If integer \(n<8\), what is its greatest possible value?
💡Integers are discrete.
Answer
\(7\).
ExampleThere is no greatest real number below \(8\), but the greatest integer is \(7\).
Prompt
What context check follows solving an inequality?
Answer
Apply stated domain restrictions such as whole, integer, or nonnegative values.
ExampleA package count cannot be \(4.5\).
Prompt
How should you check a solved inequality?
💡Use the original inequality.
Answer
Test one value inside and one value outside the proposed solution set.
ExampleFor \(x>-2\), test \(0\) and \(-3\).
Prompt
What is a common trap with variable terms on both sides?
💡Track the remaining coefficient.
Answer
Creating a negative coefficient and forgetting the reversal during final division.
ExampleMove terms to keep a positive coefficient when convenient.
Prompt
How can fractions be handled efficiently?
💡A positive multiplier preserves direction.
Answer
Multiply every term by a positive common denominator.
ExampleMultiply \(x/3+2>5\) by \(3\).
Prompt
What does a right-pointing ray represent?
💡Right means larger.
Answer
Values greater than the endpoint, with inclusion determined by the endpoint marker.
ExampleClosed at \(1\) and right means \(x\ge1\).
Prompt
What does a left-pointing ray represent?
💡Left means smaller.
Answer
Values less than the endpoint, with inclusion determined by the endpoint marker.
ExampleOpen at \(-2\) and left means \(x<-2\).
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