Cho 1 đường tròn tâm O đường kính AB. Vẽ dây cung CD vuông góc với AB tại I (I nằm giữa A và O). Lấy điểm E trên cung nhỏ BC (E khác Bvà C), AE cắt CD tại F. CMR
a, BEFI là tứ giác nội tiếp
b, AE.AF= AC²

CM BĐT 1/a+1/b>4 /a+b TÌM GTNN của M=2/xy+ 3/x^2+y^2 với x+y =1 và x y dương

Viết lại câu:

1. We only send you books after receiving the money

-> Only after the.............................

2. The only way to eliminate world terrorizmis by united opposition

-> Only by.......................

3. People have talk much but done little about it

-> Much..........................

4. You can useit as long as you like, and it won't wear out

-> No matter.........................

Viết lại câu:

1. He never suspected that the money had been stolen

-> At no time.......................

2. Although she was busy, she managed to fine the time to help me

-> Busy.........................

3. He didn't realize who he was until later

-> Only after.......................

4. They had to wai for 12 hours before their flight left

-> Only after a.........................

5. We couldn't relax until all the the guest had gone home

-> Only after...........................

Viết lại câu:

1. We should always obey our parents

-> Never....................................

2. He insisted on a full apology

-> Nothing but.............................

3. There was no precendent for the King's rezignation

-> Never before.........................

Viết lại câu:

1. It was waste of time to write that letter

-> I needn't..................................

2. Although the fish appears to be harmless, it is qiute dangerous

-> Contrary..................................

3. As I didn't know all the facts, I rang the police

->If..........................

4. She didn't work hard enough, so she lost the job

-> The reason..............................

5. I have no advice, which I can offer you

-> I have no..............................

6. It's a cross-country vehicle with five doors

-> It's a five.................................

7. I tried as hard as I could, but I just couldn't get the money

-> No matter...................................

8. Have you ever driven this kind of car?

-> Do you.........................................?

9. Who wrote this story?

-> By...........................................

10. Are you against working on Sunday?

-> Do you object................................

11. When I arrived in China. I wrote a letter home

-> On...................................

12. He is on the fìteenth page of the report he's typing

-> So far................................

13. I was on the point of leaving the house when the telephone rang

-> I was...............................

14. I never intended to help such a man

-> I never had.........................

15. Immerdiately after his arrival, things went wrong

-> No sooner..............................

16.While I strongly disappove of you behavior, I will help you this time

-> Despite....................................