jika ²log 3=a dan ³ log5=b, maka ⁴log 15=

- Logaritma -

4log 15
= log 15 / log 4
= log (5.3) / log 4
= (log 5 + log 3) / log 4
= (³log 5 + ³log 3) / ³log2²
= ( b + 1) / ( 2. 1/a)
= (b+1) / (2/a)
= (b+1) x a/2
= (ab+a) / 2

semoga membantu
-vin