-5/13 . 3/7 - 2/7 . 8/13 + 5/13 . 1/7

= 5/13 . ( -3/7 + 1/7 ) - 2/7 . 8/13

= 5/13 . -2/7 - 2/7 . 8/13

= 2/7 . ( -5/13 - 8/13 )

= 2/7 . -1

= -2/7

Tại thời điêm t, điện áp xoay chiều  u = 220 2   cos ( 100 π t - π / 2 ) V (trong đó t tính bằng giây) có giá trị  100 2 V  và đang giảm. Sau thời điểm đó 1/300 điện áp này có giá trị là

A. - 100 2 V

B. 200 V.

C. -100 V.

B. 100 3 V

Xét mạch điện xoay chiều chỉ chứa cuộn dây thuần cảm, khi dòng điện tức thời đạt giá tri cực đại thì điện áp tức thời hai đầu mạch có giá trị

A. bằng 0

B. bằng 1/4 giá trị cực đại

C. bằng 1/2 giá trị cực đại

D. cực đại

My mom often asks me to ________ my room on the weekend.

A. stay

B. volunteer

C. make

D. clean up

1. I ought to finsh some homework before I play table tennis

2. Dr Lai reminds them to clean their teeth regularly and eat sensibly

1. She was born on August 8th 1999 in New York City

2. There are 3 people in her family except her

3. Her father is a doctor at Viet duc hospital

Her mother is a teacher at Dong Da primary school

4. Her brother is an engineer at a very big company

5. Yes, she does

It was a two-week trip

1. Does he like any beans ?

2. What color is your eraser ?

3. She feels thirsty now

4. Do you feel hungry ?

5. Apple juice is Lan's favourite drink

6. What is there for lunch ?

7. Does Lan like chicken or meat ?

8. Do you go to the zoo on Sundays ?

9. Huong's favourite food is chicken soup

10. They would like a cup of coffee and a peice of cake

11. Ba has breakfast at 7 o'clock every morning

12. What do you have for lunch ?