Вычислите $$frac{left(log_613right)^2-2log_613log_639+(log_639)^2}{left(log_681right)^2}$$

$$frac{left(log_613right)^2-2log_613log_639+(log_639)^2}{left(log_681right)^2}$$$$=frac{left(log_613-log_639right)^2}{left(log_681right)^2}=frac{left(log_6frac13right)^2}{left(4cdotlog_63right)^2}=frac1{16}=0,0625$$
0,0625