| \(\sqrt A = \sqrt B \Leftrightarrow \left\{ \begin{array}{l}A \ge 0\left( { B \ge 0} \right)\\A = B\end{array} \right.\) ; \(\sqrt {{A^2}} = \sqrt {{B^2}} \Leftrightarrow \left| A \right| = \left| B \right| \Leftrightarrow A = \pm B\) |
| \(\sqrt A = \sqrt B \Leftrightarrow \left\{ \begin{array}{l}A \ge 0\left( { B \ge 0} \right)\\A = B\end{array} \right.\) ; \(\sqrt {{A^2}} = \sqrt {{B^2}} \Leftrightarrow \left| A \right| = \left| B \right| \Leftrightarrow A = \pm B\) |
