(1-log 12 по основанию 4)(1-log 12 по основанию 3)

(1 - log4(12))(1 - log3(12)) = 
= (1 - log4(4) - log4(3))(1 - log3(3) - log3(4)) =
= (1 - 1 - log4(3))(1 - 1 - log3(4)) = 
= log4(3) * log3(4) =
= log4(3) * 1/log4(3) = 1