Hàm số y=12cotx2 có đạo hàm là:
A. y'=-xsin2x2.
B. y'=-x2sinx2.
C. y'=-xsinx2.
D. y'=-xsin2x2.

Choose the best answer for the following sentence:
The candidate was successful because everybody believed in his promise of free _____________ for them. 
A. health centre                   
B. health care
C. health fare                 
D. health providing

Choose the best answer for the following sentence:
He was ashamed of the poor food which ______________ the dinner at which he begged her to join them. 
A. consisted                    
B. occupied                     
C. comprised                    
D. contained

Choose the best answer for the following sentence:
An animal perfectly in ____________ with its environment is a perfect mechanism.
A. harmony                    
B. sympathy                   
C. discord                 
D. balance

Choose the best answer for the following sentence:
_____________ the fact that it was raining, he went for a walk.
A. Although 
B. Even though 
C. Despite 
D. In spite

Choose the best answer for the following sentence:
The professor interceded _________ the authorities on my behalf 
A. at  
B. on
C. with
D. for

Tìm khẳng định đúng trong các khẳng định sau:
 liên tục trên .
 có giới hạn khi 
 liên tục trên đoạn .
A. Chỉ và  
B. Chỉ và  
C. Chỉ  
D. Chỉ

Choose the best answer for the following sentence:
That part of the country is famous __________it's pineapples. 
A. from            
B. against                   
C. for                   
D. at

A. 1.
B. .
C. 2.
D. .

Với hàm số y=-2x4+3x3-x+2 thì y' là 
A. -8x2+9x-1.
B. -16x3+9x-1.
C. -8x3+9x2-1.
D. -18x3+9x2-1.