Mathematics>Standard Multiple Choice

　　Read the following SAT test question and then click on a button to select your answer.

　　If x is greater than 0 and y is greater than 0， and if 3^(2x) = 27^(2y)， which of the following is true？

　　(A) x = y

　　(B) x = 2y

　　(C) 2x = y

　　(D) x = 3y

　　(E) 3x = y

　　Explanation

　　If x is greater than 0 and y is greater than 0， and if 3^(2x) = 27^(2y)， then rewriting 27 as 3^3 gives 3^(2x) = 27^(2y) = (3^3)^(2y) = 3^(3(2y)). It follows that 3^(2x) = 3^(3(2y)) = 3^(6y)， and so 2x = 6y. This last equation is equivalent to x = 3y.

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（编辑：马菲）