Câu hỏi của Nguyễn Văn long trọng

Câu 1a) \(\sqrt{x}=2\Leftrightarrow\sqrt{x}=\sqrt{2^2}=\sqrt{4}\Leftrightarrow x=4\)b)\(A=\sqrt{4.5}-\sqrt{9.5}+\sqrt{5}=2\sqrt{5}-3\sqrt{5}+\sqrt{5}=0\)Câu 2a)\(\left\{{}\begin{matrix}3x+y=1\\x-2y=5\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=1-3x\\x-2+6x=5\end{matrix}\right.\)\(\Leftrightarrow\left\{{}\begin{matrix}y=1-3x\\7x=7\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=1-3.1=-2\\x=1\end{matrix}\right.\)Câu trả lời: Câu 1a) \(\sqrt{x}=2\Leftrightarrow\sqrt{x}=\sqrt{2^2}=\sqrt{4}\Leftrightarrow x=4\)b)\(A=\sqrt{4.5}-\sqrt{9.5}+\sqrt{5}=2\sqrt{5}-3\sqrt{5}+\sqrt{5}=0\)Câu 2a)\(\left\{{}\begin{matrix}3x+y=1\\x-2y=5\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=1-3x\\x-2+6x=5\end{matrix}\right.\)\(\Leftrightarrow\left\{{}\begin{matrix}y=1-3x\\7x=7\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=1-3.1=-2\\x=1\end{matrix}\right.\)