Operations with Rational Expressions
Adding, subtracting, multiplying, and dividing rationals
Operations with Rational Expressions
Multiplying Rational Expressions
Steps:
- Factor everything
- Multiply numerators and denominators
- Cancel common factors
- Simplify
Dividing Rational Expressions
Multiply by the reciprocal!
Adding/Subtracting (Same Denominator)
Combine numerators, keep denominator.
Adding/Subtracting (Different Denominators)
- Find the LCD (Least Common Denominator)
- Rewrite each fraction with the LCD
- Add or subtract numerators
- Simplify
Example:
LCD =
๐ Practice Problems
1Problem 1easy
โ Question:
Multiply: (3x)/(4) ยท (8)/(9xยฒ)
๐ก Show Solution
Step 1: Multiply numerators and denominators: (3x ยท 8)/(4 ยท 9xยฒ) = (24x)/(36xยฒ)
Step 2: Simplify by canceling common factors: (24x)/(36xยฒ) = 24/(36x) = 2/(3x)
Step 3: Alternative - cancel before multiplying: (3x)/(4) ยท (8)/(9xยฒ) = (3x ยท 8)/(4 ยท 9xยฒ) Cancel 3 and 9: factor of 3 Cancel x and xยฒ: one x Cancel 8 and 4: factor of 4 = (1 ยท 2)/(1 ยท 3x) = 2/(3x)
Step 4: Find restrictions: x โ 0
Answer: 2/(3x), where x โ 0
2Problem 2easy
โ Question:
Multiply:
๐ก Show Solution
Multiply numerators and denominators:
Cancel the common factor :
Answer:
3Problem 3easy
โ Question:
Divide: (xยฒ - 4)/(x + 3) รท (x + 2)/(xยฒ + 6x + 9)
๐ก Show Solution
Step 1: Change division to multiplication: (xยฒ - 4)/(x + 3) ยท (xยฒ + 6x + 9)/(x + 2)
Step 2: Factor all expressions: xยฒ - 4 = (x + 2)(x - 2) xยฒ + 6x + 9 = (x + 3)ยฒ
Step 3: Rewrite with factors: [(x + 2)(x - 2)]/(x + 3) ยท [(x + 3)ยฒ]/(x + 2)
Step 4: Cancel common factors: Cancel (x + 2) and one (x + 3) = (x - 2) ยท (x + 3) = (x - 2)(x + 3)
Step 5: Expand (optional): = xยฒ + 3x - 2x - 6 = xยฒ + x - 6
Step 6: Find restrictions: x โ -3, -2 (from original denominators)
Answer: xยฒ + x - 6 or (x - 2)(x + 3), where x โ -3, -2
4Problem 4medium
โ Question:
Divide:
๐ก Show Solution
Step 1: Multiply by the reciprocal
Step 2: Factor everything
Step 3: Cancel and
Step 4: Multiply
Answer:
5Problem 5medium
โ Question:
Add: (2x)/(x + 1) + (3)/(x + 1)
๐ก Show Solution
Step 1: Identify that denominators are the same: Both have denominator (x + 1)
Step 2: Add numerators: (2x + 3)/(x + 1)
Step 3: Check if numerator can be factored: 2x + 3 cannot be factored
Step 4: Find restrictions: x โ -1
Answer: (2x + 3)/(x + 1), where x โ -1
6Problem 6medium
โ Question:
Subtract: (5)/(2x) - (3)/(4xยฒ)
๐ก Show Solution
Step 1: Find the LCD: Denominators: 2x and 4xยฒ LCD = 4xยฒ
Step 2: Convert to equivalent fractions: (5)/(2x) = (5 ยท 2x)/(2x ยท 2x) = (10x)/(4xยฒ) (3)/(4xยฒ) already has the LCD
Step 3: Subtract numerators: (10x)/(4xยฒ) - (3)/(4xยฒ) = (10x - 3)/(4xยฒ)
Step 4: Check if can be simplified: 10x - 3 cannot be factored with 4xยฒ
Step 5: Find restrictions: x โ 0
Answer: (10x - 3)/(4xยฒ), where x โ 0
7Problem 7hard
โ Question:
Add:
๐ก Show Solution
Step 1: Find LCD
Step 2: Rewrite with LCD
Step 3: Add numerators
Step 4: Expand and simplify
Answer:
8Problem 8hard
โ Question:
Simplify: (x)/(xยฒ - 1) + (2)/(xยฒ + 2x + 1) - (1)/(x + 1)
๐ก Show Solution
Step 1: Factor all denominators: xยฒ - 1 = (x + 1)(x - 1) xยฒ + 2x + 1 = (x + 1)ยฒ x + 1 = (x + 1)
Step 2: Find LCD: LCD = (x + 1)ยฒ(x - 1)
Step 3: Convert each fraction to LCD: x/[(x + 1)(x - 1)] = [x(x + 1)]/[(x + 1)ยฒ(x - 1)]
2/(x + 1)ยฒ = [2(x - 1)]/[(x + 1)ยฒ(x - 1)]
1/(x + 1) = [(x + 1)(x - 1)]/[(x + 1)ยฒ(x - 1)]
Step 4: Combine numerators: [x(x + 1) + 2(x - 1) - (x + 1)(x - 1)]/[(x + 1)ยฒ(x - 1)]
Step 5: Expand numerators: xยฒ + x + 2x - 2 - (xยฒ - 1) = xยฒ + 3x - 2 - xยฒ + 1 = 3x - 1
Step 6: Write final answer: (3x - 1)/[(x + 1)ยฒ(x - 1)]
Step 7: Find restrictions: x โ -1, 1
Answer: (3x - 1)/[(x + 1)ยฒ(x - 1)], where x โ -1, 1
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