a,b)

c)

Do đèn mắc nối tiếp nên: I = I₁ = I₂ = 0,5A

d)

Do đèn mắc nối tiếp nên: U = U₁ + U₂

=> U₂ = U - U₁ = 3 - 1,2 = 1,8V

Bài nào?

28 C

29 B

30 B

31 A

32 A

33 D

28 C

29 B

30 B

31 A

32 A

33 D

1. He said he hadn't got any money. 2. She said she had seen the film before. 3. Nam said he wanted to go home. 4. They said they hadn't seen their mother for years. 5. They said they couldn't come on Tuesday. 6. Sally said she didn't like chocolate. 7. Mary said she was planning to take a trip. 8. Tom said he had already eaten lunch. 9. Kate said she had called her doctor. 10. Mr. Rice said he was going to Chicago. 11. Eric said he would come to the meeting. 12. Jean said she couldn't afford to buy a new car. 13. Jessica said she might go to the library. 14. Ted said he had to finish his work. 15. Miss Young said she must talk to Professor Reed. 16. Alice said she should visit her aunt and uncle. 17. Jim said he was sleepy. 18. They said they had lunch in Lug's restaurant. 19. Susan said she was washing the car. 20. The little boy said he felt ill.

Đề bài đâu b

Câu 1: A

Câu 1:

a: ΔABC vuông tại A

=>\(AB^2+AC^2=BC^2\)

=>\(BC^2=6^2+8^2=36+64=100=10^2\)

=>BC=10

=>Chọn A

b: Xét ΔACB vuông tại A có AH là đường cao

nên \(AH\cdot BC=AB\cdot AC\)

=>\(AH\cdot10=6\cdot8=48\)

=>AH=48/10=4,8

=>Chọn B

c: ΔAHB vuông tại H

=>\(HA^2+HB^2=AB^2\)

=>\(HB^2=6^2-4,8^2=3,6^2\)

=>HB=3,6

=>Chọn B

d: Xét ΔHAB vuông tại H và ΔHCA vuông tại H có

\(\hat{HAB}=\hat{HCA}\left(=90^0-\hat{HBA}\right)\)

Do đó: ΔHAB~ΔHCA

=>\(\frac{S_{HAB}}{S_{HCA}}=\left(\frac{AB}{CA}\right)^2=\left(\frac68\right)^2=\frac{9}{16}\)

=>Chọn C

Câu 2:

a: đối và huyền

b: cos

c: cotg a>1

d: -1<=cosa<=1

Câu 3: D

Câu 4: C

Câu 6: A

Câu 7: B

a: Xét ΔABN và ΔCBM có 

BA=BC

\(\widehat{ABN}\) chung

BN=BM

Do đó: ΔABN=ΔCBM

b: Ta có: ΔABN=ΔCBM

nên BN=BM

Xét ΔBAC có BM/BA=BN/BC

nênMN//AC