Dik 2 log 3=m dan 2log 5=n maka 20 log 18 dalam m dan n

²⁰log18
= (²log18) / (²log20)
= (²log(2x9)) / (²log(4x5))
= (²log2 + ²log9) / (²log4 + ²log5)
= (²log2 + ²log3²) / (²log2² + ²log5)
= (²log2+ 2.²log3) / (2.²log2 + ²log5)
= (1 + 2m) / (2 + n)
= (2m + 1) / (n + 2)