\(1,\\ 1,ĐK:11x-2021\ge0\Leftrightarrow x\ge\dfrac{2021}{11}\\ 2,\\ A=3\sqrt{2}-10\sqrt{2}+6\sqrt{2}=-\sqrt{2}\\ B=3-\sqrt{5}+3+\sqrt{5}=6\\ C=4-3-2\cdot2=-3\\ 2,\\ 1,=\dfrac{-4\left(\sqrt{3}+\sqrt{5}\right)}{-2}=2\sqrt{3}+2\sqrt{5}\\ 2,\Leftrightarrow\left|2x+3\right|=6\Leftrightarrow\left[{}\begin{matrix}2x+3=6\\2x+3=-6\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=-\dfrac{9}{2}\end{matrix}\right.\\ 3,\left(\sqrt{26}+\sqrt{5}\right)^2=31+2\sqrt{130}\\ 7^2=49=31+18\\ 2\sqrt{130}=\sqrt{520}>\sqrt{324}=18\\ \Leftrightarrow\left(\sqrt{26}+\sqrt{5}\right)^2>7^2\\ \Leftrightarrow\sqrt{26}+\sqrt{5}>7\)
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