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exs1
1 don't have to
3 mustn't
7 don't have to
exs2
3 might
4 can't
7 might be
còn nữa ...

\(\dfrac{15,6\cdot260-156\cdot26}{15,6\cdot3,3\cdot3,4\cdot2,6}\)
\(=\dfrac{156\cdot\left(260-10\cdot26\right)}{15,6\cdot3,3\cdot3,4\cdot2,6}\)
\(=\dfrac{156\cdot0}{15,6\cdot3,3\cdot3,4\cdot2,6}\)
\(=\dfrac{0}{15,6\cdot3,3\cdot3,4\cdot2,6}\)
\(=0\)

1) Vì x=25 thỏa mãn ĐKXĐ nên Thay x=25 vào biểu thức \(A=\dfrac{\sqrt{x}-2}{x+1}\), ta được:
\(A=\dfrac{\sqrt{25}-2}{25+1}=\dfrac{5-2}{25+1}=\dfrac{3}{26}\)
Vậy: Khi x=25 thì \(A=\dfrac{3}{26}\)
2) Ta có: \(B=\dfrac{\sqrt{x}-3}{\sqrt{x}+1}+\dfrac{2x+8\sqrt{x}-6}{x-\sqrt{x}-2}\)
\(=\dfrac{\left(\sqrt{x}-3\right)\left(\sqrt{x}-2\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)}+\dfrac{2x+8\sqrt{x}-6}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)}\)
\(=\dfrac{x-5\sqrt{x}+6+2x+8\sqrt{x}-6}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)}\)
\(=\dfrac{3x+3\sqrt{x}}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)}\)
\(=\dfrac{3\sqrt{x}\left(\sqrt{x}+1\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)}\)
\(=\dfrac{3\sqrt{x}}{\sqrt{x}-2}\)

2. You didn't remember turning off the TV last night, did you?
3. The countryside suffers much less pollution than the city.
4. Why don't you go to work by bike?
6. More trees will be planted along this street.
7. Overpopulation causes a lot of social problems in this area, doesn't it?
8. Pollution is the most serious problem, isn't it?
9. Did a group of foreigners visit slums last week?
câu 1, 5, 10 thấy đã làm rồi nên mình không có làm lại nha.
2. You didn't remember turning off the TV last night, did you?
3. The countryside suffers much less pollution than the city.
4. Why don't you go to work by bike?
6. More trees will be planted along this street.
7. Overpopulation causes a lot of social problems in this area, doesn't it?
8. Pollution is the most serious problem, isn't it?
9. Did a group of foreigners visit slums last week?



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