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Algebra Foundations ยท Inequalities

Compound inequalities

Two conditions joined by AND or OR.

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Compound inequalities

A compound inequality combines two simple inequalities.

  • AND (intersection): both must hold. Example: โˆ’2 < x โ‰ค 5 is shorthand for x > โˆ’2 AND x โ‰ค 5.
  • OR (union): at least one must hold. Example: x < โˆ’1 OR x > 4.

Strategy

Solve each piece independently, then combine on a number line.

3x โˆ’ 1 > 5 AND 3x โˆ’ 1 โ‰ค 14 โ†’ x > 2 AND x โ‰ค 5 โ†’ 2 < x โ‰ค 5.

Practice

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Solve: โˆ’1 < 2x + 1 โ‰ค 7.