D thuộc tập hợp rỗng

cho mạch điện UAB khong đổi,Ra=0,

Điều chỉnh C để

+ Ia=I1=2A=> biến trở cóP1=48W

+ Ia=I2=5A=>biến trở có P2=38W

a,tính UAB và r?

b, vị trí của con trỏ để P lớn nhất và P lớn nhất=?

Mong mọi người giúp e với ak

Cho 4 gương phẳng như hình vẽ.Chính giữa gương phẳng có 1 lỗ nhỏ

1,Vẽ đường đi của tia sáng từ ngoài vào qua A.Sau khi phản xạn trên các gương G1,G2,G3,G4 rồi qua lỗ A ra ngoài

2,Tính đường đi tia sáng trên, đường đi này có phụ thuộc vào lỗ A ko

tìm x để A<0

hay -\(\frac{-\left(x^{2^{ }}+2x+5\right)}{4\left(x+1\right)}< 0\)

1 khối gỗ hình trụ có chiều dài L bán kính R

Chuyển từ câu chủ động sang câu bị động và ngược lại

M.N help em với

2.how many lesons are you going to learn

3.A leader should be a man that every one can respect

4 wwe have to put off our visit until later

5did you tell her to be here by o'clock

6 did anybody ever teach you how to behave

7 you have not done much

8.when should we turn on the program

9.the closure of the workshop will make a lot of men redundant

10.they used to help me a lot

11.I hate people looking at me

12. did he answer the last telegram or not

13,my mother came 2 days ago and they are taking good care of her

14.I should love someone to make me out tonight

15.people ought to tell us how much they expect of us

16.it is impossible to learn this poem by heart

17.she is employing a man to tile the bathroom

18.it is necessary to make the room tidy

19.it isn't necessary to type this letter

20 i want him to feed the lions

21.he didn't want anybody to recongie him

22.they should have allowed her a chane to explain herself

23the couldn't see him any where

24 i want you to type all the letters by 10 a.m

25 it is higt time someone told him to stop behaving like a child

26he expected us to offer him the job

7.they've already had a porter carry the luggage for them

28 The Prime Minister is going to open the enquiry

29.someone should have written to the newpapers

30 i must congratulate you on passing your driving test

31 they often criticize him but he doesn't seem to mind

32 no one can blae you for what happened

33they couldn't find the manager anywhere

34.he hates people asking him about his past

35.we are lokking into the matter

36. do i need to meet the new manager at the airport

37. they rumor that the couple are to seek a divorce

38 you need to cut your hair before the interview

39.the police have towed Alan's car away

40 the govrnment has called out troops

41 their house has been broken into 3 times this year