\[\begin{array}{l}
a)\,\,\,y = \frac{{2x + 1}}{{{x^2} - 6x + a - 2}}\\
K = R.\\
Ham\,\,\,so\,\,\,xac\,\,\,dinh \Leftrightarrow {x^2} - 6x + a - 2 \ne 0\,\,\,\forall x \in R\\
\Leftrightarrow pt\,\,{x^2} - 6x + a - 2 = 0\,\,\,\,vo\,\,\,nghiem\\
\Leftrightarrow \Delta ' < 0\\
\Leftrightarrow 9 - a + 2 < 0\\
\Leftrightarrow a > 11.\\
b)\,\,\,y = \frac{{x + 2a}}{{x - a - 1}}\\
K = \left( { - 1;\,\,0} \right)\\
\Rightarrow hs\,\,\,xac\,\,dinh \Leftrightarrow x - a - 1 \ne 0\,\,\,\,\forall x \in \left( { - 1;\,\,0} \right)\\
\Leftrightarrow x \ne a + 1\,\,\,\,\,\forall x \in \left( {1;\,0} \right)\\
\Leftrightarrow a + 1 \notin \left( { - 1;\,\,0} \right)\\
\Leftrightarrow \left[ \begin{array}{l}
a + 1 \le - 1\\
a + 1 \ge 0
\end{array} \right. \Leftrightarrow \left[ \begin{array}{l}
a \le - 2\\
a \ge - 1
\end{array} \right..
\end{array}\]
