Đặt \(\hept{\begin{cases}\sqrt{x+2y}=a\\\sqrt{x-2y}=b\end{cases}}\)
\(\Rightarrow\left(1\right)\Leftrightarrow a+b=\sqrt{2\left(a^2-b^2\right)}\)
\(\Leftrightarrow\left(a+b\right)^2=2\left(a^2-b^2\right)\)
\(\Leftrightarrow\left(a+b\right)\left(3b-a\right)=0\)
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