Cho 6,4g Cu tác dụng với dung dịch H₂SO₄ đặc nóng dư thu được V lít khí SO₂. Tính giá trị của V.

Tính khối lượng vôi sống thu được khi nung 100kg CaCO₃ với hiệu suất 80%

Cho các chất sau: FeS, FeS₂, FeO, Fe₂O₃.

Chất nào có hàm lượng phần trăm Fe lớn nhất?

Cho đường tròn tâm O đường kính AB, dây cung CD cắt AB ở M. Biết \(\widehat{BMP}\) = 30^o, MC = 4cm, MD = 12cm. Tính khoảng cách từ tâm đến dây CD

Cho đdường tròn tâm O và điểm M nằm bên trong đường tròn. Qua M kẻ dây AB⊥OM và dây CD không vuông góc với OM. So sánh AB và CD ( Xét 2 trùng hợp: M trùng với O và M ≠ O)

Rewrite these sentences, not to chance the meanings:

1. Please, explain this letter for me !

→ Please tell me..................................

2. It is high time for us to go home.

→ It is high time we ..........................

3. You can't go in to this restaurant without a jacket and tie.

→ Unless..............................................

4. The question was so difficult that no one could answer it.

→ It was such......................................

5. She hasn't finished the letter yet.

→ This letter........................................

6. He isn't good at English. He can't get a job.

→ If......................................................

7. Mary doesn't spend much money. She spent much last month.

→ Mary doesn't.....................................

8. The weather isn't fine. We can't go for a walk in the woods.

→ If..........................................................

9. I'll ask someone to make a new dress.

→ I'll have.................................................

10. The bridge might be built in a hurry.

→ People..............................................

11. You really should be able to dress yourself by now.

→ It's high time...................................

12. I wish I hadn't told him what we were planning to do thet evening.

→ I regret............................................

13. I have never eaten with knives and folks before.

→ This is...............................................

14. " Why don't you ask Tom for help, Mary? " Mai said

→ Mai suggested...................................

15. Ba is too young to see horror films.

→ Ba is not.............................................

16. They should quit smoking.

→ They had..........................................

17. They once started these machines by hand.

→ They used to........................................

18. He works hard and he will pass the exam.

→ If he...................................................

19. Ba is a new comer, and so was Tom.

→ Both................................................

20. This lecture bores me.

→ I am...............................................

21. This is the most delicious cake I have ever tasted.

→ I...................................................

Rewrite these sentences, not to chance the meanings:

1. It is such a heavy bike that I can't lift it up.

→ The bike................................................

2. The farmers cut the branches of the trees each week.

→ The branches.........................................

3. The sun is much hotter than the moon.

→ The moon isn't...........................................

4. Thank you for helping me carry these heavy things.

→ It was kind...............................................

5. For me - Staying at home would be better than going out tonight.

→ I'd rather.........................................................

6. Mrs Ha told Ba to carry those books back home.

→ Mrs Ha had...................................................

7. You can't understand these things because you are very young.

→ You are not.................................................

8. Oh, my good ! I have so much work to do today.

→ Wish...........................................................

9. Tom is a playwright as well as an actor.

→ Tom is not only.........................................

10. They did not finish the kitchen on Monday.

→ The kitchen...............................................

11. The last time I saw Lan was at Tam's birtday party.

→ I ..............................................................

12. What did he tell you?

→ I need to know.........................................

13. Where did they go on holiday?

→ Do you know..............................................?

14. Where is the dentist's office?

→ Could you tell me....................................?

15. How many people are there in our school?

→ We want to know......................................?

16. This shirt is too dirty for me to wear.

→ This shirt isn't.............................................

17. Boiling eggs is not difficult for me.

→ It................................................................

18. The ancient Egyptians built the pyramids.

→ The pyramids...............................................

19. Cairo is hotter than London.

→ London isn't...............................................

20. She was overweight because she ate too much meat.

→ If she.........................................................

Cho (O;R) đường kính AB. Dây CD ⊥ OA tại trung điểm M của OA

a, Tứ giác ACOD là hình gì?

b, ΔBCD là tam giác gì?