log以2为底1/25的对数乘log以3为底数1/8的对数乘log以5为底数1/9的对数
=-log2(25) * log3(8) * log5(9)
=-2log2(5) * 3log3(2) * 2log5(3)
=-12*(lg5/lg2)(lg2/lg3)(lg3/lg5)
=-12