Đạo hàm của hàm số y=cot2x là biểu thức nào sau đây?

A.  − 1 sin 2 2 x .

B.  − 2 cos 2 2 x .

C.  − 2 sin 2 2 x .

D.  2 cos 2 2 x .  

Đun nóng 0,04 mol X với lượng vừa đủ dd NaOH thu được 6,56g muối của axit hữu cơ đơn chức Y và 2,48 g ancol đa chức Z. Biết Tỉ khối của Z so với Hiđro bằng 31. Xác định CTCT của X

A. 

B. 

C.

D. 

Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions.

Super Size Me is a 2004 film by Morgan Spurlock, in which he documents his experiment to eat only McDonald's fast food three times a day, every day, for thirty days.

Spurlock made himself a short list of rules for the experiment, including an obligation to eat all of the three meals he ordered. He also had to ‘Super Size’, which means accepting a giant portion every time the option was offered to him. He ended up vomiting after the first Super Size meal he finished, after taking nearly twenty minutes to consume it.

After five days Spurlock put on almost 5kg, and he soon found himself feeling depressed, with no energy. The only thing that got rid of his headaches and made him feel better was another McDonald's meal, so his doctors told him he was addicted. More seriously, around day twenty, he started experiencing heart palpitations and one of the doctors detected liver problems. However, in spite of his doctor's advice, Spurlock continued to the end of the month and achieved a total weight gain of 11kg. His body mass index also increased from a healthy 23.2 to an overweight 27.

It took Spurlock fifteen months to recover from his experiment and return to his original weight, but the film also had a wider impact. Just after its showing in 2004, McDonald's phased out the Super Size option and healthier options like salads appeared on the menu. Unfortunately, McDonald's denied the connection between the film and the changes, but it is interesting to note how closely they coincided with the release of the film.

Question. Which of the following is the best title for the passage?

A. An experiment with McDonald's fast food

B. Putting on weight due to eating fast food

C. Connection between fast food and heart diseases

D. How fast food trigger liver damage

Cho hàm số  y = ax 3 + bx 2 + cx + d  có đạo hàm là hàm số y = f '(x) có đồ thị như hình vẽ bên. Biết rằng đồ thị hàm số y = f(x) tiếp xúc với trục hoành tại điểm có hoành độ dương. Hỏi đồ thị hàm số y = f(x)cắt trục tung tại điểm có tung độ bằng bao nhiêu?

A.  2 3 .

B. 1

C.  3 2 .

D.  4 3 .

At the moment, Ann _________ her bike to school.

A. ride    

B. is riding    

C. rides    

D. to ride

Cho hình lăng trụ tam giác đều ABC.A′B′C′ có tất cả các cạnh bằng a. Côsin góc giữa hai đường thẳng AB′ và BC bằng

A.  1 4

B.  2 4

C.  1 2

D.  3 4

A. An apartment is not as big as a villa.

B. A villa is the biggest.

C. An apartment is the smallest.

D. A villa is smaller than an apartment.

Đặt tính rồi tính 

d) 714 : 34