\begin{cases}x\geq-8\\x\geq-4\end{cases}\<=>x\geq-4\\\sqrt{x+8}-\sqrt{5x+20}=0\\\sqrt{x+8}=\sqrt{5x+20}\\x+8=5x+20\\4x=-12\\x=-3" alt="OD3:\\\begin{cases}x+8\geq0\\5x+20\geq0\end{cases}<=>\begin{cases}x\geq-8\\x\geq-4\end{cases}\<=>x\geq-4\\\sqrt{x+8}-\sqrt{5x+20}=0\\\sqrt{x+8}=\sqrt{5x+20}\\x+8=5x+20\\4x=-12\\x=-3" align="absmiddle" class="latex-formula">