10
QuizMultiple Choice

Adding and Subtracting Rational Expressions — Quiz

Question 10 • Mathematics III

What is the difference? the fraction with numerator 2 x plus 5 and denominator x squared minus 3 x minus the fraction with numerator 3 x plus 5 and denominator x cubed minus 9 x minus the fraction with numerator x plus 1 and denominator x squared minus 9

Answer
A
the fraction with numerator 3 times open paren x plus 2 close paren and denominator x squared minus 3 x
B
the fraction with numerator open paren x plus 5 close paren times open paren x plus 4 close paren and denominator x cubed minus 9 x
C
the fraction with numerator open paren x plus 5 close paren times open paren x plus 2 close paren and denominator x cubed minus 9 x
D
the fraction with numerator negative 2 x plus 11 and denominator x cubed minus 12 x minus 9

Explanation

Factor the denominators: x² − 3x = x(x − 3), x³ − 9x = x(x − 3)(x + 3), and x² − 9 = (x − 3)(x + 3). Using x(x − 3)(x + 3) as the common denominator, the combined numerator is (2x + 5)(x + 3) − (3x + 5) − x(x + 1) = x² + 7x + 10. Factoring gives (x + 5)(x + 2), so the result matches choice C.

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