Question

Difficulty: MediumEquivalent Algebraic Expressions

For all x>2x > 2, which of the following is equivalent to the expression 3x212x22x2x2+2x12x2+3x\frac{3x^2 - 12}{x^2 - 2x} - \frac{2x^2 + 2x - 12}{x^2 + 3x}?

  1. A
    x+2x\frac{x+2}{x}
  2. x+10x\frac{x+10}{x}Answer
  3. C
    x12x\frac{x-12}{x}
  4. D
    x+14x\frac{x+14}{x}

Answer

x+10x\frac{x+10}{x}
The correct answer is obtained by factoring both rational expressions and simplifying them before subtracting. The first term factors into 3(x2)(x+2)x(x2)\frac{3(x-2)(x+2)}{x(x-2)}, which simplifies to 3(x+2)x\frac{3(x+2)}{x}. The second term factors into 2(x+3)(x2)x(x+3)\frac{2(x+3)(x-2)}{x(x+3)}, which simplifies to 2(x2)x\frac{2(x-2)}{x}. Subtracting these two expressions yields 3(x+2)2(x2)x=3x+62x+4x=x+10x\frac{3(x+2) - 2(x-2)}{x} = \frac{3x+6-2x+4}{x} = \frac{x+10}{x}.

Step-by-Step Solution

1
Factor the numerators and denominators of both rational expressions.
The expression becomes 3(x2)(x+2)x(x2)2(x+3)(x2)x(x+3)\frac{3(x-2)(x+2)}{x(x-2)} - \frac{2(x+3)(x-2)}{x(x+3)}.
Factoring helps identify common binomial factors in the numerator and denominator.
2
Simplify both terms by canceling common factors.
For x>2x > 2, the expression simplifies to 3(x+2)x2(x2)x\frac{3(x+2)}{x} - \frac{2(x-2)}{x}.
Since x>2x > 2, the terms x2x-2 and x+3x+3 are non-zero and can be canceled.
3
Combine the simplified terms over the common denominator xx.
3(x+2)2(x2)x=3x+6(2x4)x\frac{3(x+2) - 2(x-2)}{x} = \frac{3x + 6 - (2x - 4)}{x}
Both terms share the common denominator xx.
4
Distribute the negative sign in the numerator and combine like terms.
3x+62x+4x=x+10x\frac{3x + 6 - 2x + 4}{x} = \frac{x+10}{x}
Distributing subtraction to the terms inside (2x4)(2x-4) yields 2x+4-2x + 4.

Key Concept

Simplifying and subtracting rational expressions by factoring and finding a common denominator
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