Jika 2log3 = a, dan 3log5 = b, maka 8log15 adalah?

[tex]^8log15= \frac{^2log15}{^2log8} \\ = \frac{^2log3\times5}{^2log2^3}\\ = \frac{^2log3+^2log5}{3\times^2log2}\\ = \frac{^2log3+^2log3\times^3log5}{3\times1}\\ = \frac{a+a\times b}{3}\\ =\frac{a+ab}{3}[/tex]