$log_27 5=\frac{1}{3}log_3 5 =a\Rightarrowlog_3 5=3alog_8 7=\frac{1}{3}log_2 7=b\Rightarrowlog_2 7=3blog_2 3=clog_6 35=\frac{log_2 35}{log_2 6}=\frac{log_2 5+log_2 7}{log_2 2+log_2 3}=\frac{\frac{log_3 5}{log_3 2}+log_2 7}{1+log_2 3}=\frac{3ac+3b}{1+c}$
log27⁡5=a" role="presentation" style="font-size: 13.696px; word-spacing: 0px; position: relative;">log27 $log
-27 5$ =
13log35=asuyralog_3 5$ =3alog27⁡5=a" role="presentation" style="font-size: 13.696px; word-spacing: 0px; position: relative;">log27 = 13 log35 =a
⇒ log35 =3a
log27 của 5 =13log35 =a suy ra log35 = 3a log87 =
13 log27 =b
⇒ log27 = 3b
log23=c
log635 =
log235log26=
log25+log27log22+log23=
log35log32+log271+log23=
3ac+3b1+c