We should be aware _______the problem facing  the world.                                               

A. of                                       

B. to                                       

C. with                                   

D. about

4. Last year, my class _______ to teach the children in a remote area.

A. volunteer                           

B. voluntary                           

C. volunteered                       

D. volunteers

5. Thomas Edison, Benjamin Franklin, James Watt are among of the greatest ____ of all time.

A. inventions                          

B. inventiveness                     

C. inventors                            

D. invents

6. Many young people carry a pair of earbuds as they are small, light, and ____.

A. chargeable                         

B. economical                        

C. portable                             

D. transferable

7. We can surf the ____ to search for news, watch films, or download music.

A. e-book                               

B. internet                              

C. laptop                                

D. smartphone

A. talent                                 

B. treatment                           

C. comment                            

D. different

cho vecto u = (2; -5) , vecto v = (3;4), vecto w = (-5 ; 7) tìm tọa độ của vecto x sao cho vecto u + 2 vecto v - 3 vecto w + vecto x = vecto 0