nhanh giúp tui với 40 điểm đó !!!!!!!!!!!!!!!!!!!!!!!!!

Một điện tích chuyển động trong điện trường theo một đường cong kín. Gọi công của lực điện trong chuyển động đó là A thì A.A > 0 nếu q > 0. B. A > 0 nếu q < 0. C. A > 0 nếu q < 0. D. A = 0. Giải thích đầy đủ, tiện cho mình hỏi đường cong kín là điện trường như thế nào

Cho $x,y,z>0$ và $xyz=1$ Chứng minh rằng: $$\frac{xy}{x^5+xy+y^5}+\frac{yz}{y^5+yz+z^5}+\frac{xz}{x^5+xz+x^5} \leq 1$$

giúp mình bài 2 và bài 5 vs mikk cảm ơn nhiều

Write the sentences using the words given 1. My sister/ like/ collect/ stamps/so/ she/ have/ big/ stamp collection. 2. They/ like/ go/ the bookstore. 3. my friends/ I/ will/ camping/ weekend. 4. Nga/ often/ read/ book/ before/ go/ bed. 5. She/ think/ read books/ interesting/ useful. 6. How/ your father/ go/ work? 7. She/ love/ read/ book. 8. They/ often/ go/ park.

Giúp mình với mn ơi, tối học r :((

Cho tam giác ABC nhọn có các đường cao BD và CE cắt nhau tại H. M là trung điểm BC. N và P lần lượt là trung điểm AH và DE. CMR: N, P, M thẳng hàng

vẽ Smiley (Tokyo Revengers) Đk:đẹp nha,nhanh,ko màu,ko phải chibi Đủ đk trên thì đc ctln,cảm ơn, vote5*

1. He was writing to his friend when he __________a noise. A. was hearing B. heard C. had heard D. hears 2. I __________many people since I came here in June. A. met B. has met C. was meeting D. have met 3. We __________ maths at this time last week. A. were learning B. are learning C. was learning D. learnt 4. She was playing games while he __________a football match. A. watched B. watches C. was watching D. watching 5. She __________to Ho Chi Minh city last year. A. goes B. has gone C. go D. went 6. Since we came here, we ______ a lot of acquaintances. A. have had B. had C. have D. are having Công ty phần mềm Cửu Long Dịch vụ thiết kế website,phần mềm CRM www.susasoft.com 26 7. __________he playing football now? A. Will B. Does C. Was D. Is 8. Every morning, I often sit in my garden and____ to my nightingale sing. A. listening B. listen C. listened D. listens 9. She __________school when she was six. A. start B. started C. has started D. are starting 10. I. __________TV when the telephone rang. A. watched B. was watching C. are watching D. have watched 11. I will contact you as soon as I ___________the information. A. will get B. get C. got D. had got 12. If he's late again, I_____ very angry. A. am going to be B. will be C. would be D. am 13. A: “The phone is ringing” B. “ I ______it”. A. answer B. will answer C. have answered D. will be answering 14. Yesterday, I _______ for work late because I _______ to set my alarm. A. had left / forgot B. was leaving / was forgetting C. left / had forgot D. had been leaving / would forget 15. By the time we ____ to the train station, Susan _____ for us for more than two hours. A. will get / has been waiting B. got / was waiting C. got / had been waiting D. get / will wait 16. While her brother was in the army, Sarah ___________ to him twice a week. A. was writing B. wrote C. has written D. had written 17. The Titanic _______ the Atlantic when it _______ an iceberg. A. was crossing / struck B. had crossed / was striking C. crossed / had struck D. is crossing / strikes 18. In the 19th century, it _______ two or three months to cross North America by covered wagon.

Giúp e vớiiiiiiii . chỉ cần khoanh thôi ạ