bài 1: chứng minh đẳng thức bằng nhau a, a( b - c )-b(a+ c)+c(a-b)=-2bc

Một hình chữ nhật có chiều dài 7/10m, chiều rộng ngắn hơn chiều dài 1/5m. Tính chu vi và diện tích của hình chữ nhật đó.

So sánh đặc điểm của vacxin vô hoạt và vacxin nhược độc. Lấy ví dụ minh họa

Giải giúp với ạ. hứa vote 5 sao

Ai khong chê ít điểm thì giúp tui với

Vẽ đậu mầm vô cảm đi NL: có bn nào để avarta đôi vs tui khum?

Criminals , slum Đặt câu đơn vs các từ trên và ghép hai câu đơn thành câu ghép :)( #MinhAnhLee @Hành

Số nghịch đảo của một số nguyên a khác 0 là : a . -a b. a c. 1/a d. -1/a

People usually sing because they like music or because they feel happy. They express their happiness by singing. When a bird sing, however, its song usually means much more than that the bird is happy. Birds have many reasons for singing. They sing to give information. Their songs are their language. The most beautiful songs are sung by male (cock) birds. They sing when they want to attract a female (hen) bird. It is their way of saying that they are looking for a wife. Birds also sing to tell other birds to keep away. To a bird, his tree or even a branch of tree, is his home. He does not want strangers to come near him, so he sings to warn them. If a bird cannot sing well, he usually has some other means of giving important information. Some birds dance, spread out their tails or make other sings. One bird has a most unusual way of finding a wife. It builds a small garden of shells and flowers. 21. Why do people usually sing ? A. They like birds. B. They feel happy. C. They want to tell a story . D. They like studying music. 22. Which birds sing the most beautiful songs ? A. Birds in a good temper. B. Cock birds. C. Hen birds. D. Female birds which attract male birds. 23. What warnings does a bird sometimes sing ? A. A warning to keep away. B. A warning to come quickly. C. A warning about the approach of people D. A warning to stop singing. 24. What do most birds usually do if they cannot sing well ? A. warn other birds to go away. B. give their information in another way. C. find a wife. D. fly high in the sky. 25. What is one bird's unusual way of attracting a hen bird ? A. It dances. B. It spreads out its tail. C. It searches for a wife. D. It uses shells and flowers to make a garden.

Chứng minh ∆MOB là tâm giác đều