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d: Ta có: \(\sqrt{6+\sqrt{11}}-\sqrt{6-\sqrt{11}}\)
\(=\dfrac{\sqrt{12+2\sqrt{11}}-\sqrt{12-2\sqrt{11}}}{\sqrt{2}}\)
\(=\dfrac{\sqrt{11}+1-\sqrt{11}+1}{\sqrt{2}}\)
\(=\sqrt{2}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
d: Ta có: \(\sqrt{6+\sqrt{11}}-\sqrt{6-\sqrt{11}}\)
\(=\dfrac{\sqrt{12+2\sqrt{11}}-\sqrt{12-2\sqrt{11}}}{\sqrt{2}}\)
\(=\dfrac{\sqrt{11}+1-\sqrt{11}+1}{\sqrt{2}}\)
\(=\sqrt{2}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(6\sqrt{x-1}-\dfrac{1}{3}\cdot\sqrt{9x-9}+\dfrac{7}{2}\sqrt{4x-4}=24\) (ĐK: \(x\ge1\))
\(\Leftrightarrow6\sqrt{x-1}-\dfrac{1}{3}\cdot\sqrt{9\left(x-1\right)}+\dfrac{7}{2}\sqrt{4\left(x-1\right)}=24\)
\(\Leftrightarrow6\sqrt{x-1}-\dfrac{1}{3}\cdot3\sqrt{x-1}+\dfrac{7}{2}\cdot2\sqrt{x-1}=24\)
\(\Leftrightarrow6\sqrt{x-1}-\sqrt{x-1}+7\sqrt{x-1}=24\)
\(\Leftrightarrow12\sqrt{x-1}=24\)
\(\Leftrightarrow\sqrt{x-1}=\dfrac{24}{12}\)
\(\Leftrightarrow\sqrt{x-1}=2\)
\(\Leftrightarrow x-1=4\)
\(\Leftrightarrow x=4+1\)
\(\Leftrightarrow x=5\left(tm\right)\)
b) \(\dfrac{1}{2}\sqrt{4x+8}-2\sqrt{x+2}-\dfrac{3}{7}\sqrt{49x+98}=-8\) (ĐK: \(x\ge-2\))
\(\Leftrightarrow\dfrac{1}{2}\cdot2\sqrt{x+2}-2\sqrt{x+2}-\dfrac{3}{7}\cdot7\sqrt{x+2}=-8\)
\(\Leftrightarrow\sqrt{x+2}-2\sqrt{x+2}-3\sqrt{x+2}=-8\)
\(\Leftrightarrow-4\sqrt{x+2}=-8\)
\(\Leftrightarrow\sqrt{x+2}=\dfrac{-8}{-4}\)
\(\Leftrightarrow\sqrt{x+2}=2\)
\(\Leftrightarrow x+2=4\)
\(\Leftrightarrow x=4-2\)
\(\Leftrightarrow x=2\left(tm\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a: Ta có: \(4\sqrt{3a}-3\sqrt{12a}+\dfrac{6\sqrt{a}}{3}-2\sqrt{20a}\)
\(=4\sqrt{3a}-6\sqrt{3a}+2\sqrt{2a}-4\sqrt{5a}\)
\(=-2\sqrt{3a}+2\sqrt{2a}-4\sqrt{5a}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a, (\(\sqrt{128}\)-\(\sqrt{50}\)+\(\sqrt{98}\)):\(\sqrt{2}\)
=(8-5+3)
=10
b, (\(\sqrt{48}\)+\(\sqrt{27}\)-\(\sqrt{192}\)):2\(\sqrt{3}\)
=(2+1,5-4)
=-0,5
c, \(\dfrac{1}{8}\)-3\(\sqrt{2}\) +\(\dfrac{1}{8}\)+3\(\sqrt{2}\)
=\(\dfrac{1}{4}\)
d, \(\sqrt{\left(1-\sqrt{5}\right)^2}-\sqrt{5}\)
=-1
![](https://rs.olm.vn/images/avt/0.png?1311)
2x2-\(2\left(2\sqrt{2}-2\right)\)x+3=\(2\sqrt{2}\)
\(\Delta'=\left(2\sqrt{2}-2\right)^2-2\left(3-2\sqrt{2}\right)\)
\(=12-8\sqrt{2}-34+24\sqrt{2}\)
\(=-22+16\sqrt{2}>0\)
=> pt có 2 nghiệm gì đấy mình chưa học cái này
b c tương tự
\(A=\sqrt{3+2\sqrt{2}}-\dfrac{1}{2}\sqrt{8}\)
\(=\sqrt{2}+1-\sqrt{2}\)
=1