Jika ⁵log3 = a dan ³log4 = b maka ⁴log15 =....

⁵Log 3  = a --> ³Log 5 = ¹/ₐ
³Log 4  = b --> ⁴Log 3 = ¹/ᵇ

⁵Log 3 x ³Log 4 = ⁵Log 4
     a     x      b     = ⁵Log 4  --> ⁵Log 4 = ab

⁴Log 15 = Log 15 / Log 4
            
               = ⁵Log 15/ ⁵Log 4
               = ⁵Log (5.3) / ⁵Log 4
               = ⁵Log 5 + ⁵Log 3 / ⁵Log 4
               = 1+a   /  ab