Giá trị của a, b sao cho phương trình sau nghiệm đúng với mọi x:   là
A. a = 1 và l b l < 2.
B. l a l > 2 và b = 1.
C. a = 1 và l b l > 2.
D. l a l < 2 và b = 1.

Đạo hàm của y=1-2x2 là
A. y'=121-2x2.
B. y'=-4x1-2x2.
C. y'=-2x1-2x2.
D. Một kết quả khác.

Choose the best answer for the following sentence:
Did you say that you _______________ here only three days ago? 
A. came   
B. have come   
C. had came   
D. come

Choose the best answer for the following sentence:
Vietnam recommended archery, vovinam, billiards-snooker and canoeing _____________ official sports at the games. 
A.  at              
B. with             
C. as                       
D. in

Choose the best answer for the following sentence:
The bee will never bite you if you _____________ it. 
A. don’t annoy               
B. wouldn't annoy
C. didn't annoy                   
D. hadn't annoyed

Với hàm số y=-2x4+3x3-x+2 thì y' là
A. -8x2+9x-1.
B. -16x3+9x-1.
C. -8x3+27x2-1.
D. -18x3+9x2-1.

Choose the best answer for the following sentence:
Weekend in my family is the time when mother and daughter cook meals whereas father and son _________ broken things around the house. 
A. make             
B. mend                 
C. correct                 
D. repair

Choose the best answer for the following sentence:
She waited _________________. 
A. at the airport anxiously for 5 hours
B. for 5 hours anxiously at the airport
C. at the airport for 5 hours anxiously
D. anxiously at the airport for 5 hours

Choose the best answer for the following sentence:
___________ you open the window, please? It is so hot in here. 
A. May                
B. Might               
C. Could                  
D. Need

Choose the best answer for the following sentence:
If there __________, the rice fields could have been more productive. 
A. had been enough water               
B. were enough water
C. would be enough water                 
D. are enough water