(以2为底125的对数＋以4为底25的对数＋以8为底5的对数﹚﹙以5为底2的对数＋以25为底4的对数＋以125为底8的

[(log2 125)+(log4 25)+(log8 5)][(log5 2)+(log25 4)+(log125 8)]=[(3log2 5)+(log2 5)+(1/3)(log2 5)][(log5 2)+(log5 2)+(log5 2)]=(13/3)(log2 5)(3)(log5 2)=13