7(x) =√4x+1-√-2+1 7(x) 2x+1phan (2x+1)(x-3) đề bài tìm tập xác định

$\begin{array}{l} f\left( x \right) = \sqrt {4x + 1} - \sqrt { - 2x + 1} \\ DK:\left\{ \begin{array}{l} 4x + 1 \ge 0\\ - 2x + 1 \ge 0 \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l} x \ge - \frac{1}{4}\\ x \le \frac{1}{2} \end{array} \right. \Leftrightarrow - \frac{1}{4} \le x \le \frac{1}{2}\\ \Rightarrow TXD:D = \left[ { - \frac{1}{4};\frac{1}{2}} \right]\\ f\left( x \right) = \frac{{2x + 1}}{{\left( {2x + 1} \right)\left( {x - 3} \right)}}\\ DK:\left\{ \begin{array}{l} 2x + 1 \ne 0\\ x - 3 \ne 0 \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l} x \ne - \frac{1}{2}\\ x \ne 3 \end{array} \right.\\ \Rightarrow TXD:D = R\backslash \left\{ { - \frac{1}{2};3} \right\} \end{array}$