1.What was he doing when you ………………………..?

A. come                       B. to come              C. came                  D. coming

2. Hanoi is  not  very ……...........................from Kuala Lumpur

A. difference                B. different              C. differ                  D. differently

3. They enjoyed …………………….. football after school .

A. played           B. to play                C. playing               D. play

4. They haven’t seen this film , ……………………… ?

A. do they                    B. have they C. don’t they D. they have

5. It rains heavily, …………………. I can’t go to the movie with you.

A. and                          B. but           C. because              D. so

B 

C

B

tìm giá trị nhỏ nhất hay lớn nhất vậy bạn?

x + 3y = 10 <=> x = 10 - 3y thay vào D ta được:

D = (10 - 3y)² + y² = 100 - 60y + 9y² + y² 

D = 10y² - 60y + 100 = 10(y² - 6y + 10) 

D = 10(y² -2y3 + 9 + 1) = 10[(y - 3)² + 1]

D = 10(y - 3)² + 10 \(\ge\)10

Dấu "=" xảy ra khi: y - 3 = 0 <=> y = 3

=> x = 10 - 3y = 10 - 3.3= 1

Vậy gtnn D = 10 khi x = 1, y = 3

B

x² + 2x - 8 = x² + 2x + 1 - 9 = (x + 1)² - 3² = (x + 1 - 3)(x + 1 +3) = (x - 2)(x + 4)

x² + 2x - 8 = x² - 2x + 4x - 8 = x(x - 2) + 4(x - 2) = (x + 4)(x - 2)

B