j

Bài làm:

Vì a,b,c khác 0 nên:

Ta có: 

  (1) (chia cả 3 vế cho abc)

Áp dụng t/c dãy tỉ số bằng nhau ta được:

=> đpcm

1 . D , 2 . C , 3 . A , 4 . D , 5 . C

1 . D , 2 . C , 3 . A , 4 . D , 5 . C1 . D , 2 . C , 3 . A , 4 . D , 5 . C1 . D , 2 . C , 3 . A , 4 . D , 5 . C1 . D , 2 . C , 3 . A , 4 . D , 5 . C1 . D , 2 . C , 3 . A , 4 . D , 5 . C1 . D , 2 . C , 3 . A , 4 . D , 5 . C1 . D , 2 . C , 3 . A , 4 . D , 5 . C1 . D , 2 . C , 3 . A , 4 . D , 5 . C1 . D , 2 . C , 3 . A , 4 . D , 5 . C1 . D , 2 . C , 3 . A , 4 . D , 5 . C1 . D , 2 . C , 3 . A , 4 . D , 5 . C1 . D , 2 . C , 3 . A , 4 . D , 5 . C1 . D , 2 . C , 3 . A , 4 . D , 5 . C

1 . D , 2 . C , 3 . A , 4 . D , 5 . C

1 . D , 2 . C , 3 . A , 4 . D , 5 . C

1 . D , 2 . C , 3 . A , 4 . D , 5 . C

1. They often do morning exercise.

2. Nam plays football for school team.

3. My sister plays the piano at the weekends.

4. I study Math, English and history on Monday.

5. We eat lunch at the school canteen at lunch time .

6. We read in the library at break time .

7. I wear uniform at school everyday .

8. Today Mai isn't wearing uniform .

9. I excited at the first day at school .

10. Susan's favorite teacher is Science teacher 

1. They often do morning exercise.

2. Nam plays football for school team.

3. My sister plays the piano at the weekends.

4. I study Math, English and history on Monday.

5. We eat lunch at the school canteen at lunch time .

6. We read in the library at break time .

7. I wear uniform at school everyday .

8. Today Mai isn't wearing uniform .

9. I excited at the first day at school .

10. Susan's favorite teacher is Science teacher