jika jika 3 log 5 = a dan 3 log 2 = b maka nilai 12 log 15 adalah

³log5 = a
³log2 = b

¹²log15
= ³log15 / ³log12
= ³log(3 . 5) / ³log(3 . 2²)
= (³log3 + ³log5) / (³log3 + ³log2²)
= (1 + a) / (1 + 2b)