Bài 4. Chứng minh rằng giá trị các biểu thức sau không phụ thuộc vào x:
a) (x-5)(2x+3)-2x(x-3)+x+7
b) x(2x+1)-x^2(x+2)+x^3-x+3

(2x –1)(4x^2 + 2x + 1)

Ex 1. Make a question for the underlined part.
1. The communal house is usually the largest building in my village.
.........................................................................................................
2. The peoples of Viet Nam are very open and friendly.

Ex 1. Rewrite the following sentence with the same meaning.
1. Her old house is bigger than her new one.
-> Her new house......................................................................................
2. No one in my class plays tennis better than Peter.
-> Peter ..................................................................................................
3. The black dress is more expensive than the white one.
-> The white dress ..................................................................................
4. According to me, English is easier than Maths.
-> According to me, Maths ........................................................................
5. Tom drives more carefully than Mary.
-> Mary ...............................................................................................

11. Gathering and hunting still play an important role in the __________of the Laha.
A. economic        A. economy           C. economical       D. economize
12__________ethnic group has a large population, the Tay or the Ede?
A. What         B. Why       C. Which             D. Who
13. Ethnic peoples in the mountains have a simple way of farming. They use basic tools
to___________the farm work.
A. check            B. work                     C. make                               D. do
14. Nick would like to know something about the ____________groups of Viet Nam when he
visited the Museum of Ethnology.
A. culture            B. cultural              C. cultured                         D. culturology
15. Which still plays ________ important role in the life of some ethnic peoples in the
mountains?                                                                                                         A. an               B. a                         C. the                                  D. no article

Vì sao cảnh quan Châu Á lại phân hóa thành nhiều đới cảnh quan, khí hậu khác nhau?