Помогите вычислить lg9 (log9 15+log9 4-log9 6)

Question

Помогите вычислить
lg9 (log9 15+log9 4-log9 6)

Answer 1

Lg 9 (log 9 15 + log 9 4 - log 9 6 ) =
= lg 9 ( log 9 (15*4) - log 9 6 ) =
= lg 9 ( log 9 (60) - log 9 6) =
= log 10 9( log 9 (60/6)) = 
= log 10 9 (log 9 (10)) =
= log 10 9 / log 10 9 = 1