3 lg2 - lg4 =

Используем свойство логарифмов: n * logₐ b = logₐ (bⁿ) и logₐ b - logₐ c = logₐ (b/c). 3 lg2 - lg4 = lg(2³) - lg4 = lg8 - lg4 = lg(8/4) = lg2 = lg2