log2 27/(log2 18-1)=log2 27/(log2 18-log2 2)=log2 27/(log2(18:2))=log2 27/log2 9=log2 3³/log2 3²=3log2 3/2log2 3=3·1/(2·1)=3/2=1,5
log2 3·log3 4=1/log3 2·log3 4=1/log3 2·log3 2²=1/log3 2·2log3 2=2
(log2 10)^-1+(log5 10)^-1=(1/log 10 2)^-1+(log10 5)^-1=log 2+log 5=log(2·5)=log 10=1 ( log10 2=log 2 ∧ log10 5=log 5 )
