kika 5log 3 =x dan 3log 4 =y, maka 4loh 15 =

5log3 = x
³log5 = 1/x
³log4 = y
⁴log3 = 1/y

⁴log15 = ³log15/³log4
= ³log(3x5)/³log4
= (³log3 + ³log5)/³log4
= (1 + 1/x)/y
= (1 + x)/xy