Câu b nha bạn.

Theo mình nghĩ thì sau ∼ 50 phút sẽ đuổi kịp kim giờ.

1. The waiters cleaned the rooms last night. 
The rooms were cleaned by the waiters last night.

2. They didn't catch the elephant again.

 The elephant wasn't catched again by them.

3. Did she buy the watch at the shop?

Was she bought the watch at the shop?

4. They built their house in 1950.
Their house were built by them in 1950.

5. Do you do the exercises last week?

Were you done the exercises last week?

6. The pupils sent the letters the day before yesterday.

The letters were sent by the pupils the day before yesterday.

7. He didn't learn the lesson two week ago
The lesson wasn't learnt by him two weeks ago.

8. Nguyen Du wrote Kieu story.

Kieu story was written by Nguyen Du.

9. She made the cake last night. 

The cake was made by her last night. 

Hiệu điện thế giữa 2 đầu dây tóc là:
 I = U / R => U = I. R = 12 . 0,5 = 6 (V).

Hình 1: x = 140
Hình 2: x = 90
            y = 120

Cho đường tròn (O;R) và một điểm A sao cho OA = R √ 2. Vẽ các tiếp tuyến AB, AC với đường tròn. Một góc xOy= 45 độ cắt đoạn thẳng AB và AC lần lượt tại D và E, DE là tiếp tuyến của đường tròn (O). Chứng minh 2/3 R<DE<R.

Bằng 0 nhé.