16Hit1600
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))?

  1. A. x/2Correct
  2. B. 2/x
  3. C. x/(2(x + 1))
  4. 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.

More Advanced Math questions

Not affiliated with the College Board. SAT is a trademark of the College Board.