Question

已知10的a次方等于20,10的b次方等于1/5,求81的a次方除9的2b次方

Answer 1

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