2009 AMC 10A 第 13 题

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13.

P=2mP = 2^mQ=3nQ = 3^n。下列哪一项对任意整数对 (m,n)(m, n) 都等于 12mn12^{mn}

Suppose that P=2mP = 2^m and Q=3n.Q = 3^n. Which of the following is equal to 12mn12^{mn} for every pair of integers (m,n)?(m, n)?

P2QP^2 Q

PnQmP^n Q^m

PnQ2mP^n Q^{2m}

P2mQnP^{2m} Q^n

P2nQmP^{2n} Q^m

答案:E
知识点:指数质因数分解
难度评级:1280
解答:

因为 12=22312 = 2^2 \cdot 312mn=22mn3mn=(2m)2n(3n)m=P2nQm. \begin{aligned} 12^{mn} &= 2^{2mn} \cdot 3^{mn} \\ &= (2^m)^{2n} \cdot (3^n)^m \\ &= P^{2n} Q^m. \end{aligned}

所以正确答案是 E

Since 12=223,12 = 2^2 \cdot 3, 12mn=22mn3mn=(2m)2n(3n)m=P2nQm. \begin{aligned} 12^{mn} &= 2^{2mn} \cdot 3^{mn} \\ &= (2^m)^{2n} \cdot (3^n)^m \\ &= P^{2n} Q^m. \end{aligned}

Thus, the correct answer is E.

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