a) $y=\sqrt{5x-2}$
Đk: $5x-2\ge0\Leftrightarrow x\ge\dfrac{2}{5}$
Txđ: $D=[\dfrac{2}{5};+\infty)$
d) $y=\sqrt{x-2}+\dfrac{1}{x-5}$
Đk: $\left\{ \begin{array}{l}x-2\ge0 \\ x-5\ne0 \end{array} \right .\Leftrightarrow \left\{ \begin{array}{l} x\ge2 \\ x\ne5\end{array} \right .$
Txđ: $D=[2;5)\cup(5;+\infty)$
b) Đk: $\left\{ \begin{array}{l} 6-x\ge0 \\ x+2\ge0 \end{array} \right .\Leftrightarrow \left\{ \begin{array}{l} x\le6\\ x\ge-2\end{array} \right .\Leftrightarrow -2\le x\le 6$
Txđ: $D=[-2;6]$
g) Đk: $\left\{ \begin{array}{l} 5-x\ge0 \\ x-1\ne0\\x+1\ge0\end{array} \right .\Leftrightarrow \left\{ \begin{array}{l} x\le 5 \\ x\ne1\\x\ge-1\end{array} \right .\Leftrightarrow \left\{ \begin{array}{l} -1\le x\le5 \\ x\ne1\end{array} \right .$
Txđ: $D=[-1;1)\cup(1;5]$
h) Đk: $\left\{ \begin{array}{l} 2x+1\ge0 \\ \dfrac{1}{5-x}\ge0\\5-x\ne0\end{array} \right .\Leftrightarrow \left\{ \begin{array}{l} x\ge\dfrac{-1}{2} \\ 5-x>0\end{array} \right .\Leftrightarrow \left\{ \begin{array}{l} x\ge\dfrac{-1}{2} \\ x<5\end{array} \right .$
$\Leftrightarrow \dfrac{-1}{2}\le x<5$
Txđ: $D=[\dfrac{1}{2};5)$
i) Đk: $\left\{ \begin{array}{l} x+5\ge0 \\ x^2-9\ne0\end{array} \right .\Leftrightarrow\left\{ \begin{array}{l} x\ge-5 \\ x\ne\pm3\end{array} \right .$
Txđ: $D=[-5;-3)\cup(-3;3)\cup(3;+\infty)$
