$\begin{array}{l} \dfrac{1}{{\left| {2x + 1} \right|}} \ge \dfrac{1}{3}\\ \Leftrightarrow \left| {2x + 1} \right| \ge 3\\ \Leftrightarrow \left[ \begin{array}{l} 2x + 1 \ge 3\\ 2x + 1 \le - 3 \end{array} \right. \Leftrightarrow \left[ \begin{array}{l} x \ge 1\\ x \le - 2 \end{array} \right.\\ \Rightarrow B = \left[ {1; + \infty } \right) \cup \left( { - \infty ; - 2} \right] \end{array}$
