\[1)\ y = 2^{x} + \lg(6 - 3x)\]
\[6 - 3x > 0\]
\[3x < 6\]
\[x < 2.\]
\[2)\ y = 3^{- x} - 2\ln(2x + 4)\]
\[2x + 4 > 0\]
\[2x > - 4\]
\[x > - 2.\]
\[3)\ y = \frac{1}{\cos{2x}}\]
\[\cos{2x} \neq 0\]
\[2x \neq \frac{\pi}{2} + \pi n\]
\[x \neq \frac{\pi}{4} + \frac{\text{πn}}{2}.\]
\[4)\ y = tg\ \frac{x}{4}\]
\[\frac{x}{4} \neq \frac{\pi}{2} + \pi n\]
\[x \neq 2\pi + 4\pi n.\]