问题 选择题 已知3m=4,3n=5,33m-2n的值为( )A.39B.2C.6425D.45 答案 33m-2n=33m÷32n=(3m)3÷(3n)2,∵3m=4,3n=5,∴原式=43÷52=64÷25=6425.故选C.