\[y = \sqrt{|x - 4| - 6}\]
\[|x - 4| - 6 \geq 0\]
\[|x - 4| \geq 6\]
\[1)\ x - 4 \geq 6\]
\[x \geq 10\]
\[2)\ x - 4 \leq - 6\]
\[x \leq - 2.\]
\[D(y) = ( - \infty; - 2\rbrack \cup \lbrack 10; + \infty).\]