Jika 2log3 =a,5log2=b,maka 15log12 adalah..

Bab Logaritma
Matematika SMA Kelas X

¹⁵log 12 = ²log 12 : ²log 15
             = (²log (2² . 3)) : (²log (3 . 5))
             = (²log 2² + ²log 3) : (²log 3 + ²log 5)
             = (2 . ²log 2 + a) : (a + 1/b)
             = (2 + a) : ((ab + 1)/b)
             = (2b + ab) / (ab + 1)
             = (ab + 2b) / (ab + 1)

(2log12)/(2log15)
= (2log4 +2log3)/(2log3 + 2log5)
=[2(1) + a]/(a + 1/b)
= (2+a)/[(ab+1)/b]
= b (2+a)/(ab+1)
= (2b + ab)/(ab + 1)