Question

Difficulty: MediumEquivalent Algebraic Expressions

For all x>5x > 5, which of the following is equivalent to the expression 3x214x53x+1x225x5\frac{3x^2 - 14x - 5}{3x + 1} - \frac{x^2 - 25}{x - 5}?

  1. 10-10Answer
  2. B
    00
  3. C
    2x2x
  4. D
    2x102x - 10

Answer

10-10
Factoring the numerators allows both rational expressions to be simplified. The first expression, 3x214x53x+1\frac{3x^2 - 14x - 5}{3x + 1}, factors as (3x+1)(x5)3x+1\frac{(3x + 1)(x - 5)}{3x + 1}, which simplifies to x5x - 5 since x>5x > 5. The second expression, x225x5\frac{x^2 - 25}{x - 5}, factors as (x5)(x+5)x5\frac{(x - 5)(x + 5)}{x - 5}, which simplifies to x+5x + 5. Subtracting the second simplified expression from the first gives (x5)(x+5)=x5x5=10(x - 5) - (x + 5) = x - 5 - x - 5 = -10. Therefore, the equivalent expression is 10-10.

Step-by-Step Solution

1
Factor the numerator of the first rational expression, 3x214x53x^2 - 14x - 5.
(3x+1)(x5)(3x + 1)(x - 5)
To find common factors that can be simplified with the denominator 3x+13x + 1.
2
Simplify the first expression, 3x214x53x+1\frac{3x^2 - 14x - 5}{3x + 1}, for x>5x > 5.
x5x - 5
Since x>5x > 5, 3x+103x + 1 \neq 0, allowing us to divide out the common factor (3x+1)(3x + 1).
3
Factor the numerator of the second rational expression, x225x^2 - 25.
(x5)(x+5)(x - 5)(x + 5)
Using the difference of squares identity, a2b2=(ab)(a+b)a^2 - b^2 = (a - b)(a + b).
4
Simplify the second expression, x225x5\frac{x^2 - 25}{x - 5}, for x>5x > 5.
x+5x + 5
Since x>5x > 5, x50x - 5 \neq 0, allowing us to divide out the common factor (x5)(x - 5).
5
Subtract the second simplified expression from the first.
(x5)(x+5)=x5x5=10(x - 5) - (x + 5) = x - 5 - x - 5 = -10
Distributing the negative sign through the parentheses and combining like terms yields the final simplified equivalent value.

Key Concept

Simplifying rational expressions by factoring and performing polynomial operations.
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