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: x2โˆ’4x+2\frac{x^2 - 4}{x + 2}

Simplifying Strategy

  1. Factor the numerator completely
  2. Factor the denominator completely
  3. Cancel common factors

Important: You can only cancel factors, not terms!

Restrictions

Values that make the denominator zero are excluded from the domain.

Example: x+3xโˆ’5\frac{x + 3}{x - 5}

Restriction: xโ‰ 5x \neq 5 (denominator would be zero)

Common Mistakes to Avoid

โŒ Wrong: x+3x=3\frac{x + 3}{x} = 3 (can't cancel terms!)

โœ“ Correct: x+3x\frac{x + 3}{x} cannot be simplified further

๐Ÿ“š Practice Problems

1Problem 1easy

โ“ Question:

Simplify: (6xยฒ)/(9x)

๐Ÿ’ก 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: 6x23x\frac{6x^2}{3x}

๐Ÿ’ก Show Solution

Factor numerator and denominator: 6x23x=3xโ‹…2x3xโ‹…1\frac{6x^2}{3x} = \frac{3x \cdot 2x}{3x \cdot 1}

Cancel the common factor 3x3x: =2x1=2x= \frac{2x}{1} = 2x

Restriction: xโ‰ 0x \neq 0

Answer: 2x2x (where xโ‰ 0x \neq 0)

3Problem 3easy

โ“ Question:

Simplify: (xยฒ - 9)/(xยฒ + 6x + 9)

๐Ÿ’ก 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: x2โˆ’9x2+6x+9\frac{x^2 - 9}{x^2 + 6x + 9}

๐Ÿ’ก Show Solution

Step 1: Factor the numerator (difference of squares) x2โˆ’9=(x+3)(xโˆ’3)x^2 - 9 = (x + 3)(x - 3)

Step 2: Factor the denominator (perfect square trinomial) x2+6x+9=(x+3)2=(x+3)(x+3)x^2 + 6x + 9 = (x + 3)^2 = (x + 3)(x + 3)

Step 3: Write and cancel (x+3)(xโˆ’3)(x+3)(x+3)=xโˆ’3x+3\frac{(x + 3)(x - 3)}{(x + 3)(x + 3)} = \frac{x - 3}{x + 3}

Restriction: xโ‰ โˆ’3x \neq -3

Answer: xโˆ’3x+3\frac{x - 3}{x + 3} (where xโ‰ โˆ’3x \neq -3)

5Problem 5medium

โ“ Question:

Simplify: (2xยฒ + 5x - 3)/(2xยฒ - 7x + 3)

๐Ÿ’ก 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)

๐Ÿ’ก 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: x3โˆ’8x2โˆ’4\frac{x^3 - 8}{x^2 - 4}

๐Ÿ’ก Show Solution

Step 1: Factor numerator (difference of cubes) x3โˆ’8=x3โˆ’23=(xโˆ’2)(x2+2x+4)x^3 - 8 = x^3 - 2^3 = (x - 2)(x^2 + 2x + 4)

Step 2: Factor denominator (difference of squares) x2โˆ’4=(x+2)(xโˆ’2)x^2 - 4 = (x + 2)(x - 2)

Step 3: Write and cancel (xโˆ’2)(x - 2) (xโˆ’2)(x2+2x+4)(x+2)(xโˆ’2)=x2+2x+4x+2\frac{(x - 2)(x^2 + 2x + 4)}{(x + 2)(x - 2)} = \frac{x^2 + 2x + 4}{x + 2}

Restrictions: xโ‰ 2,โˆ’2x \neq 2, -2

Answer: x2+2x+4x+2\frac{x^2 + 2x + 4}{x + 2} (where xโ‰ ยฑ2x \neq \pm 2)

8Problem 8hard

โ“ Question:

Simplify: (xโด - 16)/(xยณ + 2xยฒ - 8x)

๐Ÿ’ก Show Solution

Step 1: Factor numerator completely: xโด - 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