^2 log 3 = a dan ^3 log 5 = b. maka ^6 log 15

6 log 15 = 6 log 3 + 6 log 5
2 log 3 / 2 log 6 + 2 log 5 / 2 log 6
= a / 2 log 3 + 2 log 2 + 2 log 3 . 3 log 5 / 2 log 3 + 2 log 2
= a / a+1 + ab / a+1
= a+ab / a+1 = a(b+1) / a+1