10^a=20 log10(20)=a 10^b=1/5 log10(1/5)=b 81^a/9^2b=(81^a)/9^2^b=81^a/81^b=81^(a-b) a-b=log10(20)-log10(1/5)=log10(100)=2 原式=81^2=6561 如果帮到您的话,(右上角采纳)
