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八年级数学填空题一般
题目
已知3m=43^{m}=4,32mn=23^{2m-n}=2,则9n9^{n}的值为______.
知识点:幂的乘方与积的乘方、同底数幂的除法章节:第16章 整式的乘法 / 16.1 幂的运算 / 16.1.2 幂的乘方与积的乘方

答案与解析

答案

32mn=2\because 3^{2m-n}=2
32m÷3n=2\therefore 3^{2m}\div 3^{n}=2
(3m)2÷3n=2\therefore (3^{m})^{2}\div 3^{n}=2
3m=4\because 3^{m}=4
42÷3n=2\therefore 4^{2}\div 3^{n}=2
3n=8\therefore 3^{n}=8
9n=(32)n=(3n)2=82=64\therefore 9^{n}=(3^{2})^{n}=(3^{n})^{2}=8^{2}=64
故答案为:6464.

解析

32mn=2\because 3^{2m-n}=2
32m÷3n=2\therefore 3^{2m}\div 3^{n}=2
(3m)2÷3n=2\therefore (3^{m})^{2}\div 3^{n}=2
3m=4\because 3^{m}=4
42÷3n=2\therefore 4^{2}\div 3^{n}=2
3n=8\therefore 3^{n}=8
9n=(32)n=(3n)2=82=64\therefore 9^{n}=(3^{2})^{n}=(3^{n})^{2}=8^{2}=64
故答案为:6464.

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