Keep only the values that satisfy both inequalities.
Compound Inequalities: AND, OR, and Solution Sets
Decide whether to use the overlap or the union, graph the result, write interval notation, and solve compound inequalities—including all-real and empty solution sets.
01 · Watch
Lesson video
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02 · Understand
Learning targets
- Distinguish an AND intersection from an OR union.
- Graph compound inequality solution sets on a number line.
- Write compound solution sets in interval notation.
- Solve AND and OR compound inequalities and recognize all-real or empty outcomes.
03 · Vocabulary
Key definitions
Use the set language to explain why a graph is an overlap, a union, all real numbers, or empty.
- 01Compound inequality
- Two or more inequalities considered together as one solution-set question.
- 02AND compound inequality
- A number is a solution only when it satisfies both inequalities—the intersection or overlap.
- 03OR compound inequality
- A number is a solution when it satisfies either inequality—the union of the two sets.
- 04Intersection
- The values shared by two sets. On a number line, this is where the graphs overlap.
- 05Union
- Every value in either set. In interval notation, joins the intervals.
- 06Empty set
- A set with no elements, written . It occurs when an AND compound has no overlap.
04 · Apply
Worked examples
Identify AND or OR before you combine the graphs.
Keep every value in either ray and join the intervals with union.
- Subtract 6 from all three parts: .
- Divide all three parts by 2: .
- Interval notation: .
The two sets are or . Together they cover every real number.
The two requirements become and . No number can satisfy both.
05 · Avoid
Common mistakes
OR includes every value in either set, not just the shared region.
AND keeps only values that satisfy both conditions.
The inequality uses an open circle and a round parenthesis at 10.
Two separate OR intervals need ∪ between them.
Apply each legal operation to all three parts.
Disjoint regions give the empty set.
06 · Check yourself
Quick check
Decide first, then open the answer.
1Write as a chain and in interval notation.
and .
2Write in interval notation.
.
3Solve .
. Subtract 1 from all three parts, then divide all three parts by 3.
4What is the AND solution to and ?
The empty set, . The two rays do not overlap.
5What is the OR solution to or ?
All real numbers, . The union covers the entire number line.
07 · Revisit
Transcript and assigned practice
Search the corrected transcript for an example, then complete the eKadence worksheet Compound Inequalities.
Download corrected transcript