logx(27)=6
有对数定义
x^6=27=3^3=(√3)^6
底数x>0
所以x=√3
log64(x)=2/3
64^(2/3)=x
x=(4^3)^(2/3)=4^2
x=16
log2[log5(x)]=0
log2[log5(x)]=log2(1)
log5(x)=1=log5(5)
x=5