Cho 20 điểm trong đó có 6 điểm thẳng hàng. Có bao nhiêu tam giác mà các đỉnh là 3 trong 20 điểm đó.

Một tế bào sinh dục của ruồi giấm đang ở kì trung gian. a/ xác định số NST kép và số tâm động trong tế bào. b/ khi tế bào bước vào lần phân bào 1 bình thường: - số NST ở kỳ đầu là bao nhiêu? - số NST ở kỳ giữa là bao nhiêu? - số NST đang phân li về một cực tế bào là bao nhiêu?

Cho tam giác ABC, h là trực tâm .Qua B kẻ đường thẳng vuông góc với AB,Qua C kẻ đường thẳng vuông góc với AC,hai đường thẳng này cách nhau tại D a)C/m tứ giác BHCD là hình bình hành b)gọi E là điểm đx của H qua AB. C/m BC//ED

dien so thich hop vao cho cham :a)123.9 ha......km2 b)2tan 35kg.........tan c)36.9dm2......m2 d)21cm3mm.........cm

giải dùm mik 125.(-3).(-8).(-10)

giúp mình bài này với ạ. Mình cảm ơn nhiều.

tính A=1/1.2.3+1/2.3.4+1/3.4.5+......+1/18.19.20 giải thik chi tiết từng bước giải xong mik vote 5 sao cảm ơn

I. Complete the passage with the words from the box. For me TV is the best source of (1)____________. I can relax and have fun at the same time. My favourite TV (2)____________ is “How I met your mother”. I like it (3)____________ it is funny and I (4)____________ myself a lot. I watch it every day. The series follows the main character Ted Mosby, and his group of (5)____________ in Manhattan. I am also (6)____________ of “Criminal Minds” and “CSI:NY”. TV is indeed very important for me. I would go (7)____________ if I couldn’t watch it for a week. My parents sometimes have to (8)____________ my television viewing, but that’s okay. II. Choose the correct answer for each of the gaps to complete the following text. Television first came some sixty years ago in the 1950s. Nowadays, it is one of the most (1) sources of entertainment for both the old and the young. Television brings (2) for children, world news, music and many other (3) . If someone likes sports, he can just choose the right sports, (4) . It is not difficult for us to see why (5) is a TV set in almost every home today. 1. A.cheap B.expensive C.popular D.exciting 2. A.news B.cartoons C.sports D.plays 3. A.sets B.reports C.channels D.programmes 4. A.athletes B.channel C.time D.studio 5. A.it B.this C.that D.there III. Read the passage, and decide whether the sentences are true (T) or false (F). Television is an important invention of the 20 th century. It has been so popular that we can't imagine what life would be like if there were no television. Television is a major means of communication and entertainment. It brings pictures and sound from around the world into millions of homes. Through television, viewers can see and learn about people, places and things in distant lands. Television widens our knowledge by introducing new ideas which may lead us to new hobbies and recreations. In addition to the news, television provides us with a variety of programs that can satisfy every taste. Most people now seem to like spending their evenings watching television than to go out. 1. Television is an important means of communication. 2. Television provides us with a variety of programs. 3. Most people don';t like watching TV in the evening. 4. Television can';t satisfy all our tastes. 5. People can learn many things through TV. IV. Read the passages carefully. Then answer the questions. 1. Which TV programme does Steve like watching? 2. Why does Kate like watching documentaries on wildlife? 3. How much time does Rachel spend watching TV? 4. According to Rachel, what are the benefits of TV?

Cho ∆ABC vuông tại A có đường cao AH. Từ H kẻ HN vuông AC ( N thuộc AC ), kẻ HM vuông AB ( M thuộc AB ) Chứng minh : BC^2 = BD^2 + CE^2 + 2BH.HC

Bài1.(3x-2) (4x+5) = 0 Bài2.(2,3x-6,9) (0,1x+2) B3.(2x-3) (4x+5) (2x+7) =0 B4.(4x+2) (x mũ 2+1) =0 Giúp mình nha