\(\left(\dfrac{4}{\sqrt{5}+1}-\dfrac{4}{\sqrt{5}-1}\right):\sqrt{3+2\sqrt{2}}\)

\(=\left(\dfrac{4\left(\sqrt{5}-1\right)-4\left(\sqrt{5}+1\right)}{4}\right):\left(\sqrt{2}+1\right)\)

\(=\dfrac{\left(\sqrt{5}-1-\sqrt{5}-1\right)}{\sqrt{2}+1}=\dfrac{-2}{\sqrt{2}+1}=-2\left(\sqrt{2}-1\right)=-2\sqrt{2}+2\)

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B2 : NEU RA ND CUA DOAN VAN

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Cần phải có IQ vô cực

Bài 2: 

a) Ta có: \(\dfrac{5\sqrt{2}-2\sqrt{5}}{\sqrt{5}-\sqrt{2}}+\dfrac{6}{2-\sqrt{10}}-\dfrac{20}{\sqrt{10}}\)

\(=\dfrac{\sqrt{10}\left(\sqrt{5}-\sqrt{2}\right)}{\sqrt{5}-\sqrt{2}}+\dfrac{6\cdot\left(\sqrt{10}+2\right)}{\left(\sqrt{10}-2\right)\left(\sqrt{10}+2\right)}-\dfrac{\sqrt{10}\cdot2\sqrt{10}}{\sqrt{10}}\)

\(=\sqrt{10}+\sqrt{10}-2-2\sqrt{10}\)

=-2

b) Ta có: \(\left(\dfrac{5-\sqrt{5}}{\sqrt{5}}-2\right)\left(\dfrac{4}{1+\sqrt{5}}+4\right)\)

\(=\left(\sqrt{5}-1-2\right)\left(\sqrt{5}-1+4\right)\)

\(=\left(\sqrt{5}-3\right)\left(\sqrt{5}+3\right)\)

=5-9=-4

c) Ta có: \(\dfrac{\sqrt{5}-\sqrt{3}}{\sqrt{5}+\sqrt{3}}+\dfrac{\sqrt{5}+\sqrt{3}}{\sqrt{5}-\sqrt{3}}-\dfrac{\sqrt{5}+1}{\sqrt{5}-1}\)

\(=\dfrac{\left(\sqrt{5}-\sqrt{3}\right)^2+\left(\sqrt{5}+\sqrt{3}\right)^2}{\left(\sqrt{5}+\sqrt{3}\right)\left(\sqrt{5}-\sqrt{3}\right)}-\dfrac{\left(\sqrt{5}+1\right)^2}{\left(\sqrt{5}-1\right)\left(\sqrt{5}+1\right)}\)

\(=\dfrac{8-2\sqrt{15}+8+2\sqrt{15}}{2}-\dfrac{6+2\sqrt{5}}{4}\)

\(=\dfrac{16}{2}-\dfrac{6+2\sqrt{5}}{4}\)

\(=\dfrac{32-6-2\sqrt{5}}{4}\)

\(=\dfrac{26-2\sqrt{5}}{4}\)

\(=\dfrac{13-\sqrt{5}}{2}\)

Bài 3: 

c: Ta có: \(3x-5-5\sqrt{x-1}=0\)

\(\Leftrightarrow5\sqrt{x-1}=3x-5\)

\(\Leftrightarrow25x-25=9x^2-30x+25\)

\(\Leftrightarrow9x^2-55x+50=0\)

\(\text{Δ}=\left(-55\right)^2-4\cdot9\cdot50=1225\)

Vì Δ>0 nên phương trình có hai nghiệm phân biệt là:

\(\left\{{}\begin{matrix}x_1=\dfrac{55-35}{18}=\dfrac{10}{9}\\x_2=\dfrac{55+35}{18}=5\end{matrix}\right.\)

\(\text{8.C.So le trong}\)

\(\text{9.C.a trùng b}\)

\(\text{10.B.}60^0\)

\(\text{11.C.}150^0\)

\(\text{12.B.A=P}\)

1 do you do

2 had done - went

3 went - had read

4 will attend

5 hadn't worn

6 to be

7 weren't sleeping - were playing

8 to be

9 had lived - moved

10 locking

11 had work - retired 

12 told - had learned

13 won't call

14 had met

do you do

had done-went

went- had read

will attend

hadn't worn

to be