Mathematics
Grade 8
15 min
Integer inequalities with absolute values
Integer inequalities with absolute values
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1
Introduction & Learning Objectives
Learning Objectives
Define absolute value as the distance from zero on a number line.
Translate verbal descriptions into absolute value inequalities.
Solve integer inequalities of the form |x| < c and |x| ≤ c.
Solve integer inequalities of the form |x| > c and |x| ≥ c.
Represent the integer solution set of an absolute value inequality on a number line.
Interpret the solution of an absolute value inequality in a real-world context.
A professional baker needs a cake to be baked at 180°C, but the oven temperature can vary by up to 3°C. How can we describe all the acceptable integer temperatures? 🤔
This lesson will teach you how to use absolute values to solve inequalities. You'll learn how absolute value represents a distance, which is key to understanding problems...
2
Key Concepts & Vocabulary
TermDefinitionExample
IntegerA whole number that can be positive, negative, or zero. It does not have a fractional or decimal part.... -3, -2, -1, 0, 1, 2, 3 ...
Absolute ValueThe distance of a number from zero on a number line. The absolute value is always a non-negative number.The absolute value of -5, written as |-5|, is 5 because -5 is 5 units away from 0.
InequalityA mathematical statement that compares two values using symbols like < (less than), > (greater than), ≤ (less than or equal to), or ≥ (greater than or equal to).x + 2 > 7
Solution SetThe set of all the integers that make an inequality true.For x > 3, the integer solution set is {4, 5, 6, ...}.
Compound InequalityTwo inequalities joined together by the word 'and' or 'or'.'x > -2 and x...
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Core Formulas
The 'Less Than' Rule (AND Case)
If |x| < c, then -c < x < c. The same rule applies for ≤.
Use this rule when the absolute value is less than a positive number. It creates a single range of values, which is an 'and' compound inequality. Think 'less th-AND'.
The 'Greater Than' Rule (OR Case)
If |x| > c, then x > c OR x < -c. The same rule applies for ≥.
Use this rule when the absolute value is greater than a positive number. It creates two separate ranges of values, which is an 'or' compound inequality. Think 'great-OR'.
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Challenging
Find the complete integer solution set for the inequality |-x + 2| ≤ 3.
A.{-1, 0, 1}
B.{-1, 0, 1, 2, 3, 4, 5}
C.{5, 6, 7, ...}
D.{... -3, -2, -1}
Challenging
What is the solution set for the inequality |x + 4| < -1?
A.x < -5
B.x > -3
C.All integers
D.No solution
Challenging
Consider the inequalities: (I) |x| < 3 and (II) |x - 4| > 1. Which integer is a solution to both inequalities?
A.-2
B.2
C.0
D.6
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