Lesson 3: Adding & Subtracting Rational Expressions
Duration of Days: 3
Lesson Objective
Students will add and subtract rational expressions with like and unlike denominators.
• How do we add/subtract rational expressions?
• What do we need when denominators are different?
• How do we find the least common denominator?
• How is this similar to adding fractions?
Common denominator, least common denominator (LCD), numerator, denominator
CCSS.MATH.9.A.APR.D.6
Description: Students add and subtract rational expressions, first with like denominators (just add/subtract numerators), then with unlike denominators (find LCD, convert, then add/subtract). The process parallels adding fractions. Purpose: To develop procedural fluency in rational expression operations. DOK Level: 2-3 (Application)
• Start with like denominators: Easier, builds confidence
• For struggling learners: Use simple polynomials and obvious LCDs
• For advanced learners: Include complex polynomials and factoring to find LCD
• Anchor chart: Display LCD-finding strategies
• Observation: Do students find LCD correctly?
• Worksheet: Add/subtract 5 rational expressions (like denominators first)
• Practice: Add/subtract expressions with unlike denominators
• Check-your-work: Simplify the result
• Like denominator practice worksheets
• LCD-finding guides and strategies
• Unlike denominator practice worksheets
• Anchor chart for LCD
• Resource: Khan Academy "Adding & Subtracting Rational Expressions" (adapted)