Cho \(\Delta ABC\), G là trọng tâm của tam giác. Một đường thẳng d không cắt các cạnh của tam giác. Chứng minh tổng khoảng cách từ 3 đỉnh của tam giác đến d bằng 3 lần khoảng cách từ G đến d.

Change these direct questions into reported speech:

1. " Where is he ? " She asked me .............................................................................

2. " What are you doing now, Hoa ? " She asked ..............................................................

3. " Why did you go out last night ? " She asked ..............................................................

4. " Who was that beautiful woman ? " She asked ..............................................................

5. " How is your mother, Lan ? " She asked .....................................................................

6. " What are you going to do at the weekend ? " She asked ................................................

7. " Where will you live after graduation ? " She asked ..........................................................

8. " What were you doing at 8.00 yesterday ? " She asked .......................................................

9. " How was the journey ? " She asked ................................................................................

10. " How often do you go to the cinema ? " She asked ........................................................

11. " Do you live in London, John ? " She asked ....................................................................

12. " Did he arrive on time ? " She asked ................................................................................

13. " Have you been to Paris ? " She asked ..............................................................................

14. " Are you working tonight ? " She asked .............................................................................

15. " Will you come later ? " She asked .............................................................................

16. " Do you like coffee ? " She asked .............................................................................

17. " Is this the road to the station ? " She asked .............................................................................

18. " Do you do your homework everyday ? " She asked .............................................................................

19. " Have you studied reported speech before ? " She asked .............................................................................

20. " What are you going to do on Sunday next week ? " My teacher asked ........................................................

Chứng minh biểu thức sau luôn dương với mọi x:

x² + x + 3

Cho a³ + 3ab² = 63 và b³ + 3a²b = 62. Tính giá trị M = a² - b²