Jika 2log3 = a dan 3log 5 = b, nilai 15log 20 =

Jika 2log3,3log5=ab,maka 2log5=ab
Nilai 15log20=15log4.5
=15log2²+15log5
=2 15log2+15log5
2log15=2log3.5
=2log3+2log5
=a+ab
Maka 15log2=1/a+ab

5log15=5log3.5
=5log3+5log5
=1/b+1
=1+b/b
Maka 15log5=b/1+b

15log20=2 15log2+15log5
=2(1/a+ab)+b/1+b
=2/a+ab+b/1+b
=2/a+ab+ab/a+ab
=2+ab/ab