jika 5log3 = p dan 3log14 = q, maka 15log42

³log42/³log15
=³log 14.3 / ³log 3.5
=³log14+³log3 / ³log3+³log5
=q+1 / 1+1/p
=q+1 / p+1/p
=q+1. p/p+1
=p(q+1)/p+1
=pq+p / p+1

maaf kalau salah