1955 AMC 12 Problem 4

Attempt Problem 4 of the 1955 AMC 12 below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 1955 AMC 12 solutions, or check the answer key.

All problems are used with official legal permission of the Mathematical Association of America (MAA).

4.

The equality 1x−1=2x−2\dfrac1{x-1}=\dfrac2{x-2} is satisfied by:
no real values of xx
either x=1x=1 or x=2x=2
only x=1x=1
only x=2x=2
only x=0x=0
Answer: E
Concepts:rational equationdomain restrictions
Small hint:
Cross-multiply, while remembering that x≠1,2x\ne1,2
Big hint:
Solve x−2=2x−2x-2=2x-2
Solution:
For x≠1,2,x\ne1,2, cross-multiplication gives x−2=2(x−1)=2x−2, x-2=2(x-1)=2x-2, so x=0.x=0. This value makes both original denominators nonzero and satisfies the equality.
Thus, the correct answer is E.
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