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