cho hệ phương trình:(I){(a+1)x+y=4 {ax+y=2a(với a là tham số) a) Giải hệ (I) khi a=1 b)CMR:V-a,hệ luôn có nghiệm duy nhất (x;y) thỏa mãn x+y>=2

trong các giai đoạn AIDS theo em giai đoạn nào là nguy hiểm nhất ? vì sao ?

Câu 4. Cho tam giác DEF có DE = 5, EF =8 và góc DEF = 60 độ. Tinh cạnh DF và diện tích tam giác DEF. Câu 5. Cho ba điểm A(2;-3), B(4;1), C(-2:5). Tìm phương trình đường thẳng đi qua và song song với AC. Giúp mình giải câu 4 và 5 nha mn

Chọn câu trả lời tốt nhất cho những câu hỏi dưới đây Aaron's writing assignment was about an adventure. He made this chart to design his story. Use it to answer questions 1 and 2. Character Aaron (me) Tara (horse) Bram Chaxor Magus (wizard) Description brave, wise noble, black funny, rich evil, greedy, strong magical, honorable Problem must rescue friend must help Aaron wants Bram's money is asked to help Aaron Solution seek the great wizard take him places be rescued by Aaron catch him get him to help Câu 1: Which of these could Aaron use in the blank under Problem? A. good and evil B. has been captured C. adventure story D. will receive help Câu 2: This chart will help Aaron to — A. correct all of his mistakes B. understand what he reads C. plan what will happen in his story D. decide what kinds of stories he likes best Here is the first part of Aaron's rough draft. Use it to answer questions 3–5. (1) One day I woke up to some bad news. (2) My friend, Bram, had been captured by the evil Chaxor. (3) Bram was part of a nice family named the Drummonds. (4) They lived in a castle. (5) He was a regular ten-year-old kid. (6) He was a kind and friendly fellow. (7) He also liked to tell silly jokes. (8) It was horrible to think about how Bram could be trapped in Chaxor's dark cave. (9) I had to rescue my friend! (10) Something had to be done before it was too late! (11) Quickly I saddled up my noble black horse, Tara. (12) She was as fast as the wind. (13) Together we would help Bram. (14) I was deeply worried, though. (15) How could we face that evil being? (16) Chaxor had special abilities. (17) We did not have these abilities. (18) Tara was a horse with strength and courage, but she would not be successful alone. (19) I like sitting outside on warm spring nights in April. (20) As for me, I was just a young man. (21) However, I was brave and strong. Câu 3: Which of these sentences does not belong in this part of Aaron's story? A. 17 B. 18 C. 19 D. 20 Câu 4: How can sentences 6 and 7 best be joined without changing their meaning? A. He was a kind and friendly fellow also liked to tell silly jokes. B. A kind and friendly fellow also he liked to tell silly jokes. C. Was a kind and friendly fellow he also liked to tell silly jokes. D. He was a kind and friendly fellow who liked to tell silly jokes. Câu 5: Which sentence could best be added after sentence 21? A. My adventure story takes place in a land far away. B. Somehow I would find a way to defeat the evil Chaxor and free my friend. C. When I woke up, I was sad to hear the news of Bram's capture. D. Chaxor, who was an evil being, lived in a dark and ugly cave. Read this next section of Aaron's rough draft and answer questions 6–9. This section has groups of underlined words. The questions ask about these groups of underlined words. (22) There was only one person whose power was more stronger than Chaxor's. (23) This was the great wizard, Magus. (24) Magus had helped many people during his long life. (25) He was known by all in our land as being wise powerful, honorable, and fair. (26) There was only one problem. (27) Magus had been hiding from the rest of the world. (28) He lived on a mountaintop. (29) He had been betrayed by someone he trusted and had never left the mountaintop since that time. (30) I knew there was only one thing I could do. (31) Tara and I had to make a long journey. (32) We had to travel to Mount kiandra. (33) Could we get Magus to help us free Bram? (34) He was our only hope. (35) There was one thing I knew for certain. (36) Magus would never turn away someone in need. Câu 6: In sentence 25, wise powerful, honorable, should be written — A. wise, powerful, honorable, B. wise powerful honorable C. wise, powerful honorable D. as it is Câu 7: In sentence 22, was more stronger should be written — A. were stronger B. was more strong C. was stronger D. as it is Câu 8: In sentence 24, people during should be written — A. peeple during B. people durring C. peopel during D. as it is Câu 9: In sentence 31, Tara and I had to should be written — A. Tara and me had to B. I and Tara had to C. Tara and I has to D. as it is Câu 10: In sentence 32, travel to Mount kiandra should be written — A. travle to Mount kiandra B. travvel to mount Kiandra C. travel to Mount Kiandra D. as it is

Tìm số nguyên x ∈ Z biết rằng: (x ² - 1)(x ² - 4) < 0

Hai người đi xe đạp trên cùng một quãng đường. Người thứ nhất đi với vận tốc 11km/giờ, người thứ hai đi với vận tốc 215m/phút. Hỏi ai đi nhanh hơn và mỗi phút nhanh hơn bao nhiêu km?

Câu 1: tính ( 15 giờ 58 phút - 2 giờ 36 phút x 4) : 5 Câu 2 :điền đúng hoặc sai 1/2 giờ = 30 phút ..... 1 tuần 5 ngày > 13 ngày ...... 2 ngày 4 giờ > 24 giờ ..... 34 tháng < 1 năm 10 tháng ....... Câu 3 : hình chữ nhật có chiều dài là 15,5 cm ,chiều rông là 12 cm hình tròn có đường kính là 12 cm - tính chu vi cả hai hình bên - tính diện tích cả hai hình bên Câu 4:tính nhanh 20,11 : 4 + 20,11 x 0,75 trên 20,11 x 0,99 + 20,11 : 100 bài này dạng kiểu a/b nhá phân số MONG MỌI NGƯỜI GIÚP MÌNH nhanh mọi người mình đanng cần gấp

Mọi người làm rõ ràng ra dùm mình nhé đừng viết tắt ( đừng chép mạng nhé ) thanks

Các bạn ơi làm ơn giúp mình giải câu hỏi trong hình với Please