Simplifying Rational Expressions
Reducing rational expressions to simplest form
Simplifying Rational Expressions
What is a Rational Expression?
A rational expression is a fraction with polynomials in the numerator and denominator.
Example:
Simplifying Strategy
- Factor the numerator completely
- Factor the denominator completely
- Cancel common factors
Important: You can only cancel factors, not terms!
Restrictions
Values that make the denominator zero are excluded from the domain.
Example:
Restriction: (denominator would be zero)
Common Mistakes to Avoid
โ Wrong: (can't cancel terms!)
โ Correct: cannot be simplified further
๐ Practice Problems
1Problem 1easy
โ Question:
Simplify: (6xยฒ)/(9x)
๐ก Show Solution
Step 1: Factor out common factors: Numerator: 6xยฒ = 2 ยท 3 ยท x ยท x Denominator: 9x = 3 ยท 3 ยท x
Step 2: Identify GCF: GCF = 3x
Step 3: Cancel common factors: (6xยฒ)/(9x) = (2 ยท 3 ยท x ยท x)/(3 ยท 3 ยท x) = (2x)/(3)
Step 4: Restriction: x โ 0 (denominator cannot equal zero)
Answer: (2x)/3, where x โ 0
2Problem 2easy
โ Question:
Simplify:
๐ก Show Solution
Factor numerator and denominator:
Cancel the common factor :
Restriction:
Answer: (where )
3Problem 3easy
โ Question:
Simplify: (xยฒ - 9)/(xยฒ + 6x + 9)
๐ก Show Solution
Step 1: Factor the numerator: xยฒ - 9 = (x + 3)(x - 3) [difference of squares]
Step 2: Factor the denominator: xยฒ + 6x + 9 = (x + 3)ยฒ [perfect square trinomial]
Step 3: Write with factors: [(x + 3)(x - 3)]/[(x + 3)(x + 3)]
Step 4: Cancel common factor (x + 3): (x - 3)/(x + 3)
Step 5: Find restrictions: Denominator = 0 when x + 3 = 0, so x โ -3
Answer: (x - 3)/(x + 3), where x โ -3
4Problem 4medium
โ Question:
Simplify:
๐ก Show Solution
Step 1: Factor the numerator (difference of squares)
Step 2: Factor the denominator (perfect square trinomial)
Step 3: Write and cancel
Restriction:
Answer: (where )
5Problem 5medium
โ Question:
Simplify: (2xยฒ + 5x - 3)/(2xยฒ - 7x + 3)
๐ก Show Solution
Step 1: Factor the numerator using AC method: 2xยฒ + 5x - 3 Find factors of 2(-3) = -6 that add to 5: 6 and -1 2xยฒ + 6x - x - 3 = 2x(x + 3) - 1(x + 3) = (2x - 1)(x + 3)
Step 2: Factor the denominator: 2xยฒ - 7x + 3 Find factors of 2(3) = 6 that add to -7: -6 and -1 2xยฒ - 6x - x + 3 = 2x(x - 3) - 1(x - 3) = (2x - 1)(x - 3)
Step 3: Write with factors: [(2x - 1)(x + 3)]/[(2x - 1)(x - 3)]
Step 4: Cancel common factor (2x - 1): (x + 3)/(x - 3)
Step 5: Find restrictions: Original denominator = 0 when: 2x - 1 = 0 โ x = 1/2 x - 3 = 0 โ x = 3 So x โ 1/2, 3
Answer: (x + 3)/(x - 3), where x โ 1/2, 3
6Problem 6medium
โ Question:
Simplify: (xยณ - 8)/(xยฒ - 4)
๐ก Show Solution
Step 1: Factor numerator (difference of cubes): xยณ - 8 = xยณ - 2ยณ = (x - 2)(xยฒ + 2x + 4)
Step 2: Factor denominator (difference of squares): xยฒ - 4 = (x + 2)(x - 2)
Step 3: Write with factors: [(x - 2)(xยฒ + 2x + 4)]/[(x + 2)(x - 2)]
Step 4: Cancel common factor (x - 2): (xยฒ + 2x + 4)/(x + 2)
Step 5: Check if further simplification is possible: xยฒ + 2x + 4 cannot be factored (discriminant < 0)
Step 6: Find restrictions: x - 2 = 0 โ x โ 2 x + 2 = 0 โ x โ -2
Answer: (xยฒ + 2x + 4)/(x + 2), where x โ -2, 2
7Problem 7hard
โ Question:
Simplify:
๐ก Show Solution
Step 1: Factor numerator (difference of cubes)
Step 2: Factor denominator (difference of squares)
Step 3: Write and cancel
Restrictions:
Answer: (where )
8Problem 8hard
โ Question:
Simplify: (xโด - 16)/(xยณ + 2xยฒ - 8x)
๐ก Show Solution
Step 1: Factor numerator completely: xโด - 16 = (xยฒ)ยฒ - 4ยฒ [difference of squares] = (xยฒ + 4)(xยฒ - 4) = (xยฒ + 4)(x + 2)(x - 2)
Step 2: Factor denominator: xยณ + 2xยฒ - 8x = x(xยฒ + 2x - 8) = x(x + 4)(x - 2)
Step 3: Write with all factors: [(xยฒ + 4)(x + 2)(x - 2)]/[x(x + 4)(x - 2)]
Step 4: Cancel common factor (x - 2): [(xยฒ + 4)(x + 2)]/[x(x + 4)]
Step 5: This is fully simplified (no more common factors)
Step 6: Find restrictions from original denominator: x = 0, x + 4 = 0 โ x = -4, x - 2 = 0 โ x = 2 So x โ 0, -4, 2
Answer: [(xยฒ + 4)(x + 2)]/[x(x + 4)], where x โ 0, -4, 2
Practice with Flashcards
Review key concepts with our flashcard system
Browse All Topics
Explore other calculus topics