1955 AMC 12 Problem 49

Attempt Problem 49 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.

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49.

The graphs of y=x24x2y=\dfrac{x^2-4}{x-2} and y=2xy=2x intersect in:

one point whose abscissa is 22

one point whose abscissa is 00

no points

two distinct points

two identical points

Answer: C
Concepts:rational functionremovable discontinuitygraph intersection
Difficulty rating: 1400
Small Hint:

Factor x24x^2-4, but keep the original restriction x2x\ne2

Big Hint:

Compare the algebraic intersection of the simplified lines with that domain restriction

Solution:

For x2,x\ne2, x24x2=x+2. \frac{x^2-4}{x-2}=x+2. The lines y=x+2y=x+2 and y=2xy=2x would meet at x=2, y=4.x=2,\ y=4. But x=2x=2 is excluded from the original rational function, so that point is a hole and there is no intersection.

Thus, the correct answer is C.

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Problem 49 in Other Years

1950 AMC 12 · 1951 AMC 12 · 1952 AMC 12 · 1953 AMC 12 · 1954 AMC 12 · 1956 AMC 12 · 1957 AMC 12 · 1958 AMC 12 · 1959 AMC 12