`a.`\(Q=\left(\dfrac{1}{\sqrt{x}+2}+\dfrac{7}{x-4}\right):\left(\dfrac{\sqrt{x}-1}{\sqrt{x}-2}-1\right)\);\(x\ge0;x\ne4\)
\(Q=\left(\dfrac{\sqrt{x}-2+7}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}\right):\left(\dfrac{\sqrt{x}-1-\sqrt{x}+2}{\sqrt{x}-2}\right)\)
\(Q=\dfrac{\sqrt{x}+5}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}.\left(\sqrt{x}-2\right)\)
\(Q=\dfrac{\sqrt{x}+5}{\sqrt{x}+2}\)
`b.`
`@`\(x=\sqrt{27+10\sqrt{2}}-\sqrt{18+8\sqrt{2}}\)
\(x=\sqrt{\left(5+\sqrt{2}\right)^2}-\sqrt{\left(4+\sqrt{2}\right)^2}\)
\(x=\left|5+\sqrt{2}\right|-\left|4+\sqrt{2}\right|\)
\(x=5+\sqrt{2}-4-\sqrt{2}\)
\(x=1\) thế vào `Q`
\(Q=\dfrac{\sqrt{1}+5}{\sqrt{1}+2}=\dfrac{6}{3}=2\)
`@`\(x=\sqrt{\dfrac{2}{2-\sqrt{3}}}-\sqrt{\dfrac{2}{2+\sqrt{3}}}\)
\(x=\dfrac{2}{\sqrt{4-2\sqrt{3}}}-\dfrac{2}{\sqrt{4+2\sqrt{3}}}\)
\(x=\dfrac{2}{\sqrt{\left(\sqrt{3}-1\right)^2}}-\dfrac{2}{\sqrt{\left(\sqrt{3}+1\right)^2}}\)
\(x=\dfrac{2}{\left|\sqrt{3}-1\right|}-\dfrac{2}{\left|\sqrt{3}+1\right|}\)
\(x=\dfrac{2}{\sqrt{3}-1}-\dfrac{2}{\sqrt{3}+1}\)
\(x=\dfrac{2\sqrt{3}+2-2\sqrt{3}+2}{\left(\sqrt{3}-1\right)\left(\sqrt{3}+1\right)}\)
\(x=\dfrac{4}{2}=2\) thế vào `Q`
\(Q=\dfrac{\sqrt{2}+5}{\sqrt{2}+2}=\dfrac{8-3\sqrt{2}}{2}\)
