x/3 = -y/7 = k => x = 3k ; y = -7k

Thay vào:

3k.(-7k) = -189

-21k² = -189

k² = 9

k thuộc {-3;3}

k = -3 => x = -9 ; y = 21

k = 3  => x = 9 ; y = -21

D. flood nha!

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.

In most _____ developed countries, up to 50% of _____ population enters higher education at

some time in their lives.

A. Ø / Ø

B. the / Ø

C. Ø / the

D. the / a

1. There

2.works

3.buy

4.any

5.lot

6.about

7.watch

8.for

9.of

10.Who

1. went

2. watched

C nha bn!

Bn sửa lại đề đi nha, chứ câu 2 chia QKĐ là sai đó:

When ( he / arrive )

-> When did he arrived?

Where ( you / work ) before ?

-> Where have you worked before?

( They / come ) for lunch ?

-> Did they come for lunch?

1. deeply

2. difficulties

3. happiness

4.strong

5.childhood

6.flight

7. speech

8.sociable