17. The telephone was invented by Alexandar Graham Bell in 1876

18. The school gate was repainted by Nam last week

19. The train can be used a lot

20. America was discovered by Christopher in 1949

21. The accident has been seen by Minh on the road

22. The funny story was told by my father last night

23. Lam was taken to the police station by the policeman

24. This machine was repaired by Mr.Hà yesterday

25. The kitchen has kept clean by my mother

26. The eggs have eaten by the little

27. Hoa was taken to the chocolate factory by Tim yesterday

28. Our hoamework are done every day

Bài 1 : 

x²-2x+2>0 với mọi x

=x²-2.x.1/4+1/16+31/16

=(x-1/4)² + 31/16

Vì (x-1/4)² \(\ge\) 0 nên (x-1/4)² + 31/16 \(\ge\) 0 với mọi x (đfcm)