Question

Difficulty: MediumSolved 1 times0% correct100% wrongEquivalent Algebraic Expressions

For all x>3x > 3, which of the following is equivalent to the expression 2x2−5x−3x2−9−xx+3\frac{2x^2 - 5x - 3}{x^2 - 9} - \frac{x}{x+3}?

  1. x+1x+3\frac{x + 1}{x + 3}Answer
  2. B
    x−1x+3\frac{x - 1}{x + 3}
  3. C
    3x+1x+3\frac{3x + 1}{x + 3}
  4. D
    2x2−6x−3x2−9\frac{2x^2 - 6x - 3}{x^2 - 9}

Answer

x+1x+3\frac{x + 1}{x + 3}
To simplify the expression, we factor the first term: 2x2−5x−3x2−9=(2x+1)(x−3)(x−3)(x+3)\frac{2x^2 - 5x - 3}{x^2 - 9} = \frac{(2x + 1)(x - 3)}{(x - 3)(x + 3)}. Canceling the common factor of x−3x - 3 leaves 2x+1x+3\frac{2x + 1}{x + 3}. Subtracting the second term gives 2x+1x+3−xx+3=2x+1−xx+3=x+1x+3\frac{2x + 1}{x + 3} - \frac{x}{x + 3} = \frac{2x + 1 - x}{x + 3} = \frac{x + 1}{x + 3}. This matches the correct expression.

Step-by-Step Solution

1
Factor the numerator and denominator of the first rational expression.
The numerator 2x2−5x−32x^2 - 5x - 3 factors into (2x+1)(x−3)(2x + 1)(x - 3). The denominator x2−9x^2 - 9 is a difference of squares and factors into (x−3)(x+3)(x - 3)(x + 3).
Factoring allows for the simplification of the rational expression by identifying common factors in the numerator and denominator.
2
Simplify the first rational expression by canceling the common factor.
(2x+1)(x−3)(x−3)(x+3)=2x+1x+3\frac{(2x + 1)(x - 3)}{(x - 3)(x + 3)} = \frac{2x + 1}{x + 3} for all x>3x > 3.
Since x>3x > 3, the term x−3x - 3 is non-zero, allowing us to divide both the numerator and denominator by x−3x - 3.
3
Subtract the second expression from the simplified first expression.
2x+1x+3−xx+3=2x+1−xx+3=x+1x+3\frac{2x + 1}{x + 3} - \frac{x}{x + 3} = \frac{2x + 1 - x}{x + 3} = \frac{x + 1}{x + 3}
Since both fractions now have the same denominator, x+3x + 3, we subtract their numerators.

Key Concept

Simplifying rational expressions by factoring polynomials and performing operations on fractions with common denominators.
Estimated Time:1m 30s
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