2n+7chia hết n+1 3n+7chia hết 2n+1

Cho tam giác ABC vuông tại A. Trên tia BC lấy điểm D sao cho BD=BA.Đường vuông góc với cạnh BC tại D cắt AC tại E,cắt BA tại F. a)Chứng minh tam giác ABE=tam giác DBE b)Chứng minh tam giác CEF cân c)Chứng minh AD//CF Làm giúp mình với!

GT danh lam thắng cảnh tượng đài Trần Hưng Đạo, hồ Vị Xuyên

1. Margie was an _______ traveller; even dangerous conflict would not stop her from visiting a place. A. intrepid B. inquisitive C. ingenious D. insightful 2. The floral bouquets we entered into the competition were a _______ of colour, but unfortunately, we did not win first prize. A. wham B. riot C. drop D. buzz 3. Don’t forget to _______ your sources; you don’t want to get accused of stealing information. A. quote B. cite D. name D. refer 4. Travelling to Norway and experiencing the Nothern Lights first hand was always at the very top of Mary’s _______ list. A. luggage B. lag C. basket D. bucket 5. The football fans were coming in _______ to watch the final game. An hour before the kickoff the stadium was packed full. A. fingers and thumbs B. bits and bobs C. dribs and drabs D. bibs and tuckers

TÌm điều kiện của x để giá trị của biểu thức được xác định và chứng minh rằng với điều kiện đó giá trị biểu thức không phụ thuộc vào giá trị của biến ($\frac{x}{x^{2}-25}$ - $\frac{x-5}{x^{2}+5x}$) : $\frac{2x-5}{x^{2}+5x}$ + $\frac{x}{5-y}$

1. Kitchell says the city was a _______ of all American culture during the '60s. A. microclimate B. microcopy C. microcosm D. microscope 2. The idea of a nap in the middle of the day is quite _______ to British people. A. foreign B. distant C. remote D. unheard 3. The island of Tahiti _______ sandy beaches and crystal clear water. A. brags B. gloats C. boasts D. swaggers 4. I don't like intellectual novels, serious music or films; my tastes are quite ______ A. flat-topped B. lowbrow C. shamefaced D. slow-witted 5. A lot of older people are ______ because they've been complaining all their lives A. irate B. crotchety C. indignant D. infuriated

1. I know she is a bit miserable at the moment, but she’ll soon ______ up when she finds out that I have booked us a two-week holiday in Barbados. A. perk B. look C. pump D. joy 2. There is no need to get so ______ about being turned down. There are other advertising agencies out there, you know. A. destitute B. descendant C. despondent D. despicable 3. All he has done since losing his job is ______ around the house all day. A. mourn B. depress C. mope D. wallow 4. He likes nothing better than to spend his Sunday mornings ______ in the gardens. A. pottering about B. hanging around C. whiling away D. winding down 5. The three tours are run _______ so we can only choose one. A. concurrently B. recurrently C. concurringly D. cursively

1. Apart from one or two ______ of brilliance from Owen, England put on a rather poor performance. A. flashes B. spells C. storms D. strokes 2. The police believe Morgan strangled his girlfriend in a ______ of jealousy. A. burst B. fit C. flash D. spell 3. Normally, when he was late, he gave a pathetic excuse, but not this time, what he said had a ______ of truth about it. A. figment B. glimmer C. ring D. shred 4. Having gained a ______ victory in the general elections, they proceeded with their ambitious programme. A. galloping B. staunch C. landslide D. close-up 5. We can’t buy it. We have already $400 ______ at the bank. We would run up huge debts. A. overspent B. overtaken C. overdrawn D. overdone 6. It is hoped that this meeting will pave the way for ______ peace. A. long-lasting B. long-running C. long-standing D. long-winded 7. Naturally, her parents were thrilled to ______ when they found out she had passed the exam with an. A. shreds B. heaven C. goodness D. bits

Mấy bạn giải thích vì sao O2, H2, Na k tác dụng với F2 vậy ?

Cho tam giác ABC vuông tại A, tia phân giác của góc ACB cắt AB tại D.Vẽ DE vuông góc với BC tại E. a) Chứng minh: ACD = ECD. b) Gọi F là giao điểm của DE và AC.Chứng minh: BE=AF. c) Chứng minh: CD  AE.