Hai người đi bộ ngược chiều nhau từ hai địa điểm A và B cách nhau 20 km để gặp nhau. Vận tốc của người đi từ A là 4 km/giờ. Vận tốc của người đi từ B là 6 km/giờ. a) Hỏi sau mấy giờ họ gặp nhau? b) Khi gặp nhau người đi từ A cách B mấy ki-lô mét?

so sánh phong trào cách mạng 1905-1908 và cuộc khởi nghĩa xi pay

Nêu tính chất hóa học của phenol

Một ô tô đi từ tỉnh A lúc 6 giờ và đến tỉnh B lúc 10 giờ 45 phút. Ô tô đi với vận tốc 46km/giờ và nghỉ dọc đường mất 30 phút. Tính độ dài quãng đường từ tỉnh A đến tỉnh B?

Nồng độ $PO4^{3-}$ trong dung dịch Na3PO4 0,1M là:

cho tam giác abc vuông tại a đường cao ah (ab<ac) . chứng minh ac^2-ab^2=hc^2-hb^2 GIÚP MIK VS Ạ MIK CẦN GẤP Ạ

1. I still can't believe it! My bicycle_________last night. A was stolen B.was stealing C.stolen D.stole 2. The current constitutional problem is_____ the to legal minds in the country A studying B. being studying C. being studied D. been studied 3. Something funny_______ in class yesterday. A. happened B. was happened C. happens D. is happened 4. The child's arm was swollen because he______by a bee. A. stung B.had stung C. had been stung D.had being stung 5. Today, many serious childhood diseases______ by early immunization A. are preventing B. can prevent C. prevent D. can be prevented 6. I________ with you on that subject A. am agree B. am agreed C.agreeing D. agree 7. Many US automobiles_________in Detroit, Michigan A. manufacture B. have manufacture C. are manufactured D. are manufacturing 2. Let's go ahead and do it now. Nothing ______by waiting. A. accomplishes B. accomplished C. has accomplished D. will be accomplished 9. "When________ ?" “ In 1928.” A. penicillin was discovered B. did penicillin discovered C was penicillin discovered D. did penicillin discover 10. In recent years, the government has imposed pollution controls on automobile manufacturers. Both domestic and important automobiles must _____ anti-pollution devices. A equip with B.be equip with C. equip by D. be equipped by 11. A shortage of water is a problem in many part of the world. In some areas, water ______ from ground faster than nature can replenish the supply A. is being taken B. has been taken C. is taking D. has taken 12. Vitamin C_______by the human body. It gets into the bloodstream quickly A. absorbs easily B. is easily absorbing C. is easily absorbed D. absorbed easily 13. "When can I have my car back? "I think is’ll___________late this afternoon A.finish B. be finished C. have finished D. be finish 14. I didn't think my interview went very well, but I guess it must have. Despite all my anxiety, i _______for the job I wanted. I'm really going to work hard to justify their confidence. A. was hiring B. hired C. got hiring 15. be finish 15.My country ____________the pursuit of world peace. A. is dedicating to B. is dedicated to C. is dedicating by D. is dedicated by 16. About 15,000 years ago, northern Wisconsin__________under ice a mile deep A. buried B. was burying C. was buried D.had burrieed 17. Ed was new on the job, but he quickly fit himself into the______routine of the office A. established B. establishing C. establishes D. establish 18. The Mayan Indians__________an accurate and sophisticated calendar more than seven centuries ago. A. were developed B developed C. are developed D. have been developed 19. George is_______ Lisa. A. marry with B. marry to C. married with D. married to 20. The rescuers_______for their bravery and fortitude in locating the lost mountain climbers. A. were praised B. praised C. were praising D. praising Mk đag cần gấp chỉ cần viết A,B.C,D thôi nha

Chia động từ ở thì hiện tại tiếp diễn

Cho M = { 1; 13 ; 21 ; 29 ; 52 } Tìm x,y thuộc M sao cho 30< x - y < 40

Xác định hệ số a và b: a) x^4 + ax^2 + b chia hết cho x^2 - x + 1 b) ax^3 + bx^2 + 5x - 50 chia hết cho x^2 + 3x - 10