Đáp án:
Giải thích các bước giải:
Cm công thức :: (x-y)^2 lớn hoặc bằng 0
Suy ra : x^2+y^2>=2xy
suy ra (x+y)^2>=4xy
Suy ra 1/x+1/y>=4/(x+y)
Áp dụng 1/a+1/b>=4/2√2=√2
Dấu =xảy ra khi a=b=√2
Cm công thức : $(x-y)^2 ≥0$
$⇒$ $x^2+y^2≥2xy$
$⇒(x+y)^2≥4xy$
$⇒$ $\dfrac{1}{x}+\dfrac{1}{y}≥\dfrac{4}{(x+y)} $
Áp dụng :$\dfrac{1}{a}+\dfrac{1}{b}≥\dfrac{4}{2}\sqrt{2}=\sqrt{2}$
Dấu $=$ xảy ra khi $a=b=\sqrt{2}$
Giúp mình bài toán này với. Mình đang cần gấp. Cảm ơn nhìu
em hãy viết đoạn văn khoảng 7 đến 10 câu để nói lên quan điểm của em về vấn đề : Con cháu có nên tiếp nối nghề nghiệp truyền thống của gia đình dòng họ ''
IV. Choose the best vvord or phrase (A, B, C or D) to complete each sentence. 16. When you ride your bike on the streets, you should follow the directions of the ___ A. bus stop B. traffic lights C. railway station D. palace 17. I want to see famous paintings, so I'm going to visit a (n) ____ at the weekend. A. art gallery B. temple C. cathedral D. square 18. My father took me to the ____ to commemorate the national heroes. A. bridge B. stadium C. statue D. memorial 19. I couldn't have a trip to Hoi An Ancient Town because I caught a cold last week. That was so ____ for me. A. convenient B. quiet C. simple D. terrible 20. He likes living in Da Nang City because the people here are ____ hospitable. A. incredibly B. inconveniently C. noisily D. busily 21. She doesn't likes moving in the rush hours because the traffic is so ____. A. heavy B. large C.diffìcult D. exciting 22. First _____the second left. Then go ____ ahead. You will see the museum. A. turn/ away B. take/ straight C. go/ right D. pick/ left 23. ____ can I get to 899 Café? - Go to the end of Hong Bang Road. It's____ your right. A. Where/ on B. Where/ In C. How/ on D. How/ in 24. Ho Chi Minh City has ____ streets than Da Lat City. A. crovvded B. much crowded C. more crowded D. crowdedly 25. I like the atmosphere in Can Tho. It’s ____ than in Ha Noi. A. more quiet B. quieter C. quiet D. quietly 26. The weather in Binh Thuan seems to be ____ than that in Nha Trang. A. very hot B. more hot C. so hot D. hotter 27. She thinks the hotels in Hue are ____ than those in Sa Pa, A. comfortable B. very comfortable C. little comfortable D. more comfortable 28. The price of this red hat is 2$, and the price of the green hat is 4$. We can say that the green hat is ____ than the red one. A. cheaper B. more cheaper C. more expensive D. so expensive 29. Lan prefers English to maths because she thinks maths is ____ than English A. more difficult B. easier C. more easy D. very difficult 30. She gets an A mark in physics test today. It makes her feel ____ yesterday. A. very boring B. more boring C. moie happy D. happier
Chuyển các câu sau sang thể phủ định và nghi vấn
Tính tổng. ‐3 bé hơnx và lớn hơn giá trị tuyệt đối của x
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Giải phương trình sau: $x(x-2)^2-5=(x-3)^3-2(x-1)_{}$
Giúp mik đi xin m.nnnnnnnnnnnnnnnn
Tính: x-1/x-y-1-y/y-x A.2 B.x-y+2/x-y C.1 D.x+y/x-y Nêu cách giải: ...?
I. Choose the word (A, B, C or D) whose stress is different from the others. 1. A. pleasure B. hurry C. arrive D. statue 2. A. decide B. railway C. temple D. palace 3. A. restaurant B. terrible C. gallery D. expensive 4. A. capital B. pagoda C. countryside D. motorbike 5. A. direction B. afternoon C. cathedral D. fantastic II. Choose the word (A, B, C or D) whose underlined part is pronounced differently 6. A. historic B. bicycle C. fantastic D. peaceful 7. A. street B. live C. slim D. inside 8. A. market B. city C. leave D. pretty 9. A. building B. sleepy C. village D. traffic 10. A. capital B. countryside C. expensive D. police III. Choose the correct form of the words (A, B, C or D) to complete the sentences. 11. Ha Noi is a _______Capital. There are a lot of famous, ancient museums, pagodas or temples. A. historical B. history C. historic D. historically 12. He bought a new car in order to move ________ in a big city. A. conveniently B. convenient C. convenience D. inconvenient 13. The environment in our city is _____ with a lot of dirty gases from private cars. A. polluted B. polluting C. pollution D. pollutant 14. I like enjoying clean air and ______in the countryside. A. peacefully B.peaceful C. peace D. peacefulness 15. The apartment is so expensive for me____________ . A. buying B. to buy C. bought D. buys
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