Câu 1:
\(1,\\ a,=\sqrt{28,9\cdot90}=\sqrt{2601}=51\\ b,=\dfrac{\sqrt{15}}{5}\\ 2,ĐK:4x+16\ge0\Leftrightarrow x\ge-4\\ 3,\\ a,3\sqrt{2}=\sqrt{18}>\sqrt{15}\\ b,=6-2\cdot3-2=-2\)
Câu 2:
\(1,\\ a,=6\sqrt{3}+8\sqrt{3}-3\sqrt{3}=11\sqrt{3}\\ b,=\dfrac{\sqrt{5}+\sqrt{3}+\sqrt{5}-\sqrt{3}}{5-3}=\dfrac{2\sqrt{5}}{2}=\sqrt{5}\\ 2,\\ A=\dfrac{x\sqrt{x}-3x-x\sqrt{x}-3x}{\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)}\cdot\dfrac{-\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)}{\sqrt{3}\sqrt{x}}\\ A=\dfrac{6x}{\sqrt{3}\sqrt{x}}=2\sqrt{3x}\)
\(3,\Leftrightarrow2x-3=7\Leftrightarrow x=5\)
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