2006 AMC 10A Problem 6

Below is the professionally curated solution for Problem 6 of the 2006 AMC 10A, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2006 AMC 10A solutions, or check the answer key.

All of the real AMC 8, AMC 10, AMC 12, and AIME problems in our complete solution collection are used with official legal permission of the Mathematical Association of America (MAA).

Concepts:exponentalgebraic manipulation

Difficulty rating: 1190

6.

What non-zero real value for xx satisfies (7x)14=(14x)7?(7x)^{14} = (14x)^7?

17\dfrac{1}{7}

27\dfrac{2}{7}

11

77

1414

Solution:

Taking the seventh root of both sides gives (7x)2=14x,(7x)^2 = 14x, so 49x2=14x.49x^2 = 14x. Since x0,x \neq 0, divide by xx to get 49x=14,49x = 14, hence x=27.x = \dfrac{2}{7}.

Thus, the correct answer is B.

Problem 6 in Other Years