log2^(1/25)·log3^(1/8)·log5^(1/9) ＝log2^[5^(－2)]·log3^[2^(－3)]·log5^[3^(－2)] ＝(－2)·(－3)·(－2)·log2^5·log3^2·log5^3 ＝－12·(lg5/lg2)·(lg2/lg3)·(lg3/lg5) ＝－12