Lúc 7h sáng mot xe oto chạy từ điểm A, chuyển động đều với vận tốc v1=20km/h đi về phía B với khoảng cách 60km. Sau 30p, mot xe thứ 2 khởi hành từ phía B về A với vận tốc không đổi 40km/h.
Tìm thởi điểm hai xe gặp nhau.
Chú ý: Xét theo trường hợp: Gốc tọa độ tại A; Chiều từ B đến A; thời gốc thời gian: khi xe B xuất phát
Cho tam giác ABC cân tại A có cạnh đáy nhỏ hơn cạnh bên nội tiếp đường tròn (O). Tiếp tuyến tại B và C của đường tròn lần lượt cắt tia AC và AB ở D a)Chứng minh tứ giác OBDC nội tiếp b) Đường thẳng BD và AC cắt nhau tại E. Chứng minh ED2 =EC.EA c) Từ điểm M trn6 cung nhỏ BC kẻ MI vuông góc với BC, MH vuông góc AB MF vuông góc AC. C/m H,I,F thẳng hàng d)Cho góc BAC=30 độ, tính theo R diện tích tứ giác ABDC
This is the body paragraph from an essay on social networking. There are FIVE mistakes in the text. They are either grammatically incorrect or do not fit in with the sense of the text. For questions 51-55, find and underline the mistakes and write your corrections in the spaces given below the text. The task begins with an example (0).
Example: (0) arguing → arguments
Social Networking Sites
One of the main (0)arguing against social networking sites is that people sometimes reveal information on them that often should be kept private. Recently, another development has provided more support for this argument: College admissions committees are now using social networking sites as part of the application process. According with a survey by Kaplan Test Prep (2010), over 80 percent of college admissions officers use social networking sites to communicate with students. The claiming that many colleges make is that they use these sites to attract new students or to stay in contact with former students. However, some colleges admit that they are also using social networking as part of the admissions process. The main argument for using social media is that it helps colleges evaluate candidates at a time when these colleges are experiencing large numbers of applicants. Many admissions officers believe that colleges need all the information they can get on applicants in order to make decisions because the admissions process has become very competitively. One college interviewer in a recent survey reported that if she has to choose between two students who are equally qualified in terms of grades and test scores, she looks at their online profiles to make the final decision. In addition, applicants also use social networking sites against each other. Another admissions officer revealed that his office often receives anonymous messages with links to sites that have negative information on or pictures of other applicants. Many colleges and universities have not had official policies yet on whether to use social media as part of the application process. Until these policies will become clearer, prospective college students should keep their social networking pages private or remove anything that might make them look more attractive to admissions committees.
(adapted from Grammar and Beyond 4 by John D. Bunting, Luciana Diniz, &Randi Reppen© Cambridge)