tolong jawab ya secepatnya. thankyou.

15log20 = (3log20)/(3log15)
= (3log2.2.5)/(3log3.5)
= (3log2 + 3log2 + 3log5) / (3log3 + 3log5)
= (1/a + 1/a + b)/(1 + b)
= (2/a + b)/(1 + b) . a/a
= (2 + ab) / a(1 + b)