jika diketahui 3log2 = x dan 2log5 = y, maka nilai 6log15 adalah

[tex] \frac{2 log 15}{2 log 6} = \frac{2 log 5 x 2log3}{2log2x2log3} = \frac{y + \frac{1}{x} }{1 + \frac{1}{x} } [/tex]

[tex] ^{6} log 15 = \frac{log 15}{log 6} [/tex]
= [tex] \frac{log (3 x 5)}{log (2 x 3)} [/tex]
= [tex] \frac{ ^{2}log 3 + ^{2} log 5 }{ ^{2}log 2 + ^{2}log 3 } [/tex]
= [tex] \frac{ \frac{1}{x} +y}{1 + \frac{1}{x} } [/tex]
= [tex] \frac{1 + xy}{1 + x} [/tex]