3) \(4\sqrt{27b}-5\sqrt{48b}+\frac14\sqrt{192b}\)

Вынесем множители из-под корней:

\(\sqrt{27b}=3\sqrt{3b}\), \(\sqrt{48b}=4\sqrt{3b}\), \(\sqrt{192b}=8\sqrt{3b}\).

\(4\sqrt{27b}-5\sqrt{48b}+\frac14\sqrt{192b}=12\sqrt{3b}-20\sqrt{3b}+2\sqrt{3b}=-6\sqrt{3b}\).

Ответ: \(-6\sqrt{3b}\).