2 log 3 = a dan 3 log 5 = b nilai 15 log 20 =... tolong bantu kak sama caranya ya

15log 20
= ³log 20 / ³log 15
= ³log (2²×5) / ³log (3×5)
= ³log 2² + ³log 5 / ³log 3 + ³log 5
= 2 ³log 2 + ³log 5 / 1 + ³log 5
= 2(1/a) + b / 1 + b
--------------------------- × a
= (2 + ab) / (a + ab)
= (2+ab) / a(1+b)