Advanced MathVery hardDividing one rational expression by another
Advanced Math practice question
For x ≠ 0 and x ≠ −1, which expression is equivalent to (3/(x + 1)) ÷ (6/(x² + x))?
- A. x/2Correct
- B. 2/x
- C. x/(2(x + 1))
- D. (x + 1)/2
Answer: A. x/2
Dividing by a fraction is multiplying by its reciprocal: 3/(x + 1) · (x² + x)/6. Factor x² + x = x(x + 1); the (x + 1) cancels and 3/6 = 1/2, leaving x/2.
Why the other answers are wrong
- B. 2/x
- 2/x is the reciprocal of the answer — the division was set up the wrong way round.
- C. x/(2(x + 1))
- x/(2(x + 1)) forgets that the (x + 1) in the first denominator cancels with the (x + 1) inside x² + x.
- D. (x + 1)/2
- (x + 1)/2 cancels the x instead of the (x + 1): x² + x = x(x + 1), and it is the (x + 1) that matches the denominator.
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