Cô Tuyết Ngọc
Các bạn 2k5 chuẩn bị thi THPTQG 2023 hãy thử sức mình với những đề thi thử trên dgnl.olm.vn nhé.___Kỳ thi tốt nghiệp THPT có nội dung thi nằm trong chương trình giáo dục THPT hiện hành, chủ yếu là chương trình lớp 12; đề thi được xây dựng đáp ứng yêu cầu của Kỳ thi, bảo đảm độ phân hóa phù hợp và hạn chế học tủ, học lệch, khuyến khích sáng tạo của thí sinh.Các bài thi thử của OLM-ĐGNL cung cấp có cấu trúc tương tự với các bài thi chính thức, giúp các sĩ tử có đánh giá chính xác nhất học lực hiện...
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Cô Tuyết Ngọc
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Cô Tuyết Ngọc
28 tháng 3 2023 lúc 16:47

Hướng dẫn thí sinh tham gia thi thử trên OLM-ĐGNL: https://dgnl.olm.vn/tin-tuc/huong-dan-hoc-sinh-tham-gia-thi-thu-tren-olm-dgnl-643823112

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Bảo Chu Văn An
28 tháng 3 2023 lúc 17:23

2k9 làm thử được không cô nhỉ :)

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NGUYỄN LÊ TUYẾT My
28 tháng 3 2023 lúc 19:27

cooooo câu này làm sao vậy???

hãy nới một câu về bổn phận học tập của mình lớp 5

 

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violet
Xem chi tiết
Komorebi
15 tháng 4 2021 lúc 9:47

1:  Only with careful environmental planning can we protect the world in which we live.

D.  We can protect the world we live in only with careful environmental planning.

2:  You should take regular exercises instead of sitting in front of the television all day.

A.  Taking regular exercises is better than sitting in front of the television all day.

3:  It was not until after I got home that I realized I had not set the burglar alarm in the office.

C.  I didn’t turn the burglar alarm on before I left the office, but I only became aware of this after I'd arrived home.

4:  He did not remember the meeting. He went out for a coffee with his friends then.

D.  Not remembering the meeting, he went out for a coffee with his friends.

5:  They left their home early. They didn’t want to miss the first train.

C.  They left their home early so as not to miss the first train.

6:  I’m sure Luisa was very disappointed when she failed the exam

B.  Luisa must have been very disappointed when she failed the exam.

7.  “You had better see a doctor if the sore throat does not clear up.” she said to me.

D.  She suggested that I see a doctor if the sore throat did not clear up.

8:  Without her teacher’s advice, she would never have written such a good essay

C.  She wrote a good essay as her teacher gave her some advice.

9.  She tried very hard to pass the driving test. She could hardly pass it.

C.  No matter how hard she tried, she could hardly pass the driving test.

10. Mary loved her stuffed animal when she was young. She couldn’t sleep without it.

A. When Mary was young, she loved her stuffed animal so much that she couldn't sleep without it.

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Đỗ Thanh Hải
15 tháng 4 2021 lúc 0:00

1:  Only with careful environmental planning can we protect the world in which we live.

A.  Careful environmental planning protects the world we live in.

B.  Planning the environment carefully, we can protect the world in which we live.

C.  Protecting the world we live in, we plan the environment carefully.

D.  We can protect the world we live in only with careful environmental planning.

2:  You should take regular exercises instead of sitting in front of the television all day.

A.  Taking regular exercises is better than sitting in front of the television all day.

B.  Sitting in front of the television all day helps you take regular exercises.

C.  Sitting in front of the television all day and taking exercises are advisable.

D.  Don’t take regular exercises, just sit in front of the television all day.

3:  It was not until after I got home that I realized I had not set the burglar alarm in the office.

A.  On the way home, I suddenly realized that I had forgotten to turn on the burglar alarm in the office.

B.  Fortunately, I realized that I hadn't set the burglar alarm just before I left for home; otherwise, I would have had to travel all the way back to the office.

C.  I didn’t turn the burglar alarm on before I left the office, but I only became aware of this after I'd arrived home.

D. I wish I had realized before I arrived home that I hadn't turned on the burglar alarm in the office, then it would have been easier to go and set it.

4:  He did not remember the meeting. He went out for a coffee with his friends then.

A.  Not remember the meeting, he went out for a coffee with his friends.

B.  Not to remember the meeting, he went out for a coffee with his friends.

C.  Not remembered the meeting, he went out for a coffee with his friends.

D.  Not remembering the meeting, he went out for a coffee with his friends.

5:  They left their home early. They didn’t want to miss the first train.

A.  They left their home early so as to not miss the first train.

B.  They left their home early for fear that they wouldn’t miss the first train.

C.  They left their home early so as not to miss the first train.

D.  They left their home early in order that not to miss the first train.

6:  I’m sure Luisa was very disappointed when she failed the exam

A.  Luisa must be very disappointed when she failed the exam.

B.  Luisa must have been very disappointed when she failed the exam.

C. Luisa may be very disappointed when she failed the exam.

D. Luisa could have been very disappointed when she failed the exam.

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Lê Phương Thúy
15 tháng 4 2021 lúc 9:43

1:  Only with careful environmental planning can we protect the world in which we live.

D.  We can protect the world we live in only with careful environmental planning.

2:  You should take regular exercises instead of sitting in front of the television all day.

A.  Taking regular exercises is better than sitting in front of the television all day.

3:  It was not until after I got home that I realized I had not set the burglar alarm in the office.

C.  I didn’t turn the burglar alarm on before I left the office, but I only became aware of this after I'd arrived home.

4:  He did not remember the meeting. He went out for a coffee with his friends then.

D.  Not remembering the meeting, he went out for a coffee with his friends.

5:  They left their home early. They didn’t want to miss the first train.

 

C.  They left their home early so as not to miss the first train.

D.  They left their home early in order that not to miss the first train.

6:  I’m sure Luisa was very disappointed when she failed the exam

B.  Luisa must have been very disappointed when she failed the exam.

 

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Thầy Cao Đô
Xem chi tiết
emhoc24
21 tháng 6 2023 lúc 17:14

so sánh 1990^10 +1990^0 và 1991^10

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7A2- Trần Thị Quỳnh Anh
22 tháng 6 2023 lúc 5:40

Tìm nộidung của ngữ liệu sau 

Sương trắng rỏ đầu cành như giọt sữa 

Tia nắng tía chảy hoài trên ruộng lúa núi uốn mình trong chiếc áo the xanh 

Đồi thoa son nằm dưới ánh bình minh

 

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phungngoca22
Xem chi tiết
Mai Tiến Đỗ
13 tháng 12 2023 lúc 10:41

\(\int\limits^2_0\left[f\left(x\right)-2g\left(x\right)\right]dx=\int\limits^2_0f\left(x\right)dx-2\int\limits^2_0g\left(x\right)dx=3+2=5\)

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Xem chi tiết
Đoàn Trần Quỳnh Hương
25 tháng 6 2023 lúc 10:22

Cảm ơn sự nhiệt tình của anh vì gần đến kì thi THPTQG đã đăng rất nhiều học liệu có ích về môn Văn. Thật ra mấy đề của các tỉnh hên xui sẽ có thể trúng vào bài thi THPTQG nên cứ xem qua các đề tỉnh một chút biết đâu bất ngờ. 

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Nguyễn Trần Thành Đạt
25 tháng 6 2023 lúc 9:47

XEM THÊM - [NHỮNG ĐIỀU CẦN BIẾT KHI HỌC VĂN TRONG GIAI ĐOẠN NƯỚC RÚT]:  https://hoc24.vn/cau-hoi/nhung-dieu-can-biet-khi-hoc-van-trong-giai-doan-nuoc-rutday-la-kinh-nghiem-ca-nhan-cua-anh-pop-trong-giai-doan-nuoc-rut-hoc-mon-ngu-van-on-thi-thptq.8086541123947

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Mẫn Nhi
25 tháng 6 2023 lúc 14:13

Tham khảo một số đề thi gợi ý đáp án :

 ( Ngữ Văn )https://huongnghiep.hocmai.vn/dap-an-goi-y-de-thi-mau-ky-thi-tot-nghiep-thpt-2023-mon-ngu-van/

- https://huongnghiep.hocmai.vn/dap-an-goi-y-de-thi-mau-ky-thi-tot-nghiep-thpt-2023-tat-ca-cac-mon/ . - Tất cả các môn .

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Xem chi tiết
Nguyễn Trần Thành Đạt
3 tháng 4 2023 lúc 19:21

Các bạn lớp nhỏ hơn tham gia là cũng được hí, sẽ có sửa chi tiết nha!

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trần vũ hoàng phúc
3 tháng 4 2023 lúc 19:23

yeuyeu

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ᴳᵒᵈ乡anime♕
3 tháng 4 2023 lúc 20:35

Ở một loài thú, tính trạng màu lông do một gen có 2 alen quy định, trong đó lông đỏ trội hoàn toàn  so với lông trắng. Khi cho một cá thể lông đỏ giao phối với một cá thể lông trắng, thu được F1 có tỉ lệ 1 cá thể lông đỏ: 1 cá thể lông trắng. Cho F1 giao phối tự do, thu được đời F2 có tỉ lệ 1 cá thể lông đỏ : 1 cá thể lông  trắng. Biết rằng, không có đột biến xảy ra và sự biểu hiện màu lông không phụ thuộc vào môi trường. Có bao  nhiêu phát biểu dưới đây đúng? 

I. Gen quy định tính trạng màu lông nằm trên NST thường. 

II. Gen quy định tính trạng màu lông có thể nằm trên vùng không tương đồng của NST X.

III. Gen quy định tính trạng màu lông có thể nằm trên vùng tương đồng của NST X và Y.

IV. Nếu F2 tiếp tục giao phối ngẫu nhiên thì đời F3 sẽ có tỉ lệ kiểu hình 7 lông đỏ : 9 lông trắng. 

A. 4. B. 1. C. 3. D. 2. 

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violet
Xem chi tiết
Đỗ Thanh Hải
13 tháng 4 2021 lúc 21:26

Question 1. The young girl has great experience in nursing. She has worked as a hospital volunteer for years.

A. Before she worked as a hospital volunteer for years, the young girl has great experience in nursing.

B. Much as she has worked as a hospital volunteer for years, the young girl has great experience in nursing.

C. Having worked as a hospital volunteer for years, the young girl has great experience in nursing.

D. With great experience in nursing, the young girl has worked as a hospital volunteer for years.

Question 2. Peter told us about his leaving the school. He did it on his arrival at the meeting.

A. Only after his leaving the school did Peter inform us of his arrival at the meeting.

B. Not until Peter told us that he would leave the school did he arrive at the meeting.

C. Hardly had Peter informed us about his leaving the school when he arrived at the meeting.

D. No sooner had Peter arrived at the meeting than he told us about his leaving the school.

Question 3. He was successful because he was determined to pursue personal goals. He was not talented.

A. In addition to his determination, his talent ensured his success in pursuing his goals.

B. His determination to pursue personal goals made him successful and talented.

C. It was his determination to pursue personal goals, not talent, that contributed to his success.

D. His success lay in his natural ability, not in his determination to pursue personal goals.

Question 4. There was a serious flood. All local pupils couldn’t go to school on that day.

A. The serious flood prevented all local pupils not go to school on that day.

B. The serious flood hindered all local pupils from going to school on that day.

C. The serious flood made all pupils from not going to school on that day.

D. The serious flood caused all local pupils not go to school on that day.

Question 5. He did not remember the meeting. He went out for a coffee with his friends then.

A. Not remember the meeting, he went out for a coffee with his friends.

B. Not to remember the meeting, he went out for a coffee with his friends.

C. Not remembered the meeting, he went out for a coffee with his friends.

D. Not remembering the meeting, he went out for a coffee with his friends.

Question 6. They left their home early. They didn’t want to miss the first train.

A. They left their home early so as to not miss the first train.

B. They left their home early for fear that they wouldn’t miss the first train.

C. They left their home early so as not to miss the first train.

D. They left their home early in order that not to miss the first train.

Question 7. My sisters used to get on with each other. Now they hardly speak.

A. My sisters were once close, but they rarely speak to each other now.

B. My sisters do not speak to each other much, but they are good friends.

C. My sisters rarely speak because they have never liked each other.

D. Because they have never got on, my sisters do not speak to each other.

Question 8. The soccer team knew they lost the match. They soon started to blame each other.

A. Not only did the soccer team lose the match but they blamed each other as well.

B. No sooner had the soccer team started to blame each other than they knew they lost the match.

C. As soon as they blamed each other, the soccer team knew they lost the match.

D. Hardly had the soccer team known they lost the match when they started to blame each other.

A. Being friends for years, we find it quite easy to share secrets.

B. We find it quite easy to share secrets, being friends for years.

C. We have been friends so that it is quite easy to share secrets between us.

D. Having been friends for years, we find it quite easy to share secrets between us.

Question 10. I started training to be an accountant six months ago. I’ve got more months to go and then I have to take exams.

A. By the time I’ve taken my exam, I will have started training to be an accountant for a year.

B. By the time I take my exam, I will have been in training to be an accountant for a year.

C. By the time I took my exam, I would have trained to be an accountant for a year.

D. By the time I’ve taken my exam, I will be training for a year.

Question 11. The government knows the extent of the problem. The government needs to take action soon.

A. The government knows the extent of the problem whereas it needs to take action soon.

B. The government knows the extent of the problem so that it needs to take action soon.

C. Knowing the extent of the problem, the government needs to take action soon.

D. The government knows the extent of the problem, or else it needs to take action soon.

Question 12. The substance is very toxic. Protective clothing must be worn at all times.

A. Since the substance is very toxic, so protective clothing must be worn at all times.

B. So toxic is the substance that protective clothing must be worn at all times.

C. The substance is such toxic that protective clothing must be worn at all times.

D. The substance is too toxic to wear protective clothing at all times.

Question 13. I accepted the new job after all. It is making me feel exhausted.

A. Perhaps I shouldn’t have accepted this new job, as it’s making me feel exhausted.

B. Perhaps it would have been better if I hadn’t agreed to this new job since it is so boring.

C. It is of deep regret that I didn’t turn down the job offer due to its hardship and long hour work.

D. If it had not been for my acceptance the new job offer, I wouldn’t have felt exhausted.

Question 14. Since 1970, the United Nations has been celebrating April 22nd as Earth Day. It attracts millions of people worldwide to join in to promote public awareness of environmental protection.

A. Since 1970, the UNs has been celebrating April 22nd as Earth Day because it attracts millions of people worldwide to join in to promote public awareness of environmental protection.

B. The UNs has been celebrating April 22nd as Earth Day, which millions of people worldwide are attracted to join in it to promote public awareness of environmental protection.

C. Since 1970, the UNs has been celebrating April 22nd as Earth Day, which attracts millions of people worldwide to join in to promote public awareness of environmental protection.

D. Since 1970, the UNs has been celebrating April 22nd as Earth Day so that more people join in to promote public awareness of environmental protection.

Question 15. We found the bad weather very inconvenient. We chose to find a place for the night.

A. The bad weather prevented us from driving any further.

B. Bad weather was approaching, so we started to look for a place to stay.

C. Seeing that the bad weather had set in, we decided to find somewhere to spend the night.

D. Because the climate was so severe, we were worried about what we’d do at night.

Question 16. He held the rope with one hand. He stretched it out.

A. The rope is held with one hand then he stretched it out.

B. Stretching the rope out, he holds it with one hand.

C. Holding the rope with one hand, he stretched it out.

D. He stretched the rope with one hand and held it.

Question 17. The plan may be ingenious. It will never work in practice.

A. Ingenious as it may be, the plan will never work in practice.

B. Ingenious as may the plan, it will never work in practice.

C. The plan may be too ingenious to work in practice.

D. The plan is as impractical as it is ingenious.

Question 18. I never received the letter. It was sent to the wrong address.

A. Since it was sent to the wrong address, I have never received the letter.

B. I never received the letter because it was sent to the wrong address.

C. I never received the letter because of sending to the wrong address.

D. Sent to wrong address, I never received the letter.

Question 19. In your country, schools are open to all. They accept children of any race, colour or creed.

A. In our country, schools are open to all children irrespective of race, colour or creed.

B. In our country, schools are open to all children except for race, colour or creed.

C. Apart from race, colour or creed, schools are open to all children in your country.

D. Children of any race, colour or creed can be admitted to our schools when they are opened.

Question 20. He felt very tired. He was determined to continue to climb up the mountain.

A. He felt so tired that he was determined to continue to climb up the mountain.

B. Feeling very tired, he was determined to continue to climb up the mountain.

C. Tired as he might, he was determined to continue to climb up the mountain.

D. As a result of his tiredness, he was determined to continue to climb up the mountain.

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Question 1. The young girl has great experience in nursing. She has worked as a hospital volunteer for years.

ABefore she worked as a hospital volunteer for years, the young girl has great experience in nursing.

B. Much as she has worked as a hospital volunteer for years, the young girl has great experience in nursing.

C. Having worked as a hospital volunteer for years, the young girl has great experience in nursing.

D. With great experience in nursing, the young girl has worked as a hospital volunteer for years.

Question 2. Peter told us about his leaving the school. He did it on his arrival at the meeting.

A. Only after his leaving the school did Peter inform us of his arrival at the meeting.

B. Not until Peter told us that he would leave the school did he arrive at the meeting.

C. Hardly had Peter informed us about his leaving the school when he arrived at the meeting.

D. No sooner had Peter arrived at the meeting than he told us about his leaving the school.

Question 3. He was successful because he was determined to pursue personal goals. He was not talented.

A. In addition to his determination, his talent ensured his success in pursuing his goals.

B. His determination to pursue personal goals made him successful and talented.

C. It was his determination to pursue personal goals, not talent, that contributed to his success.

D. His success lay in his natural ability, not in his determination to pursue personal goals.

Question 4. There was a serious flood. All local pupils couldn’t go to school on that day.

A. The serious flood prevented all local pupils not go to school on that day.

B. The serious flood hindered all local pupils from going to school on that day.

C. The serious flood made all pupils from not going to school on that day.

D. The serious flood caused all local pupils not go to school on that day.

Question 5. He did not remember the meeting. He went out for a coffee with his friends then.

A. Not remember the meeting, he went out for a coffee with his friends.

B. Not to remember the meeting, he went out for a coffee with his friends.

C. Not remembered the meeting, he went out for a coffee with his friends.

D. Not remembering the meeting, he went out for a coffee with his friends.

Question 6. They left their home early. They didn’t want to miss the first train.

A. They left their home early so as to not miss the first train.

B. They left their home early for fear that they wouldn’t miss the first train.

C. They left their home early so as not to miss the first train.

D. They left their home early in order that not to miss the first train.

Question 7. My sisters used to get on with each other. Now they hardly speak.

A. My sisters were once close, but they rarely speak to each other now.

B. My sisters do not speak to each other much, but they are good friends.

C. My sisters rarely speak because they have never liked each other.

D. Because they have never got on, my sisters do not speak to each other.

Question 8. The soccer team knew they lost the match. They soon started to blame each other.

A. Not only did the soccer team lose the match but they blamed each other as well.

B. No sooner had the soccer team started to blame each other than they knew they lost the match.

C. As soon as they blamed each other, the soccer team knew they lost the match.

D. Hardly had the soccer team known they lost the match when they started to blame each other.

A. Being friends for years, we find it quite easy to share secrets.

B. We find it quite easy to share secrets, being friends for years.

C. We have been friends so that it is quite easy to share secrets between us.

D. Having been friends for years, we find it quite easy to share secrets between us.

Question 10. I started training to be an accountant six months ago. I’ve got more months to go and then I have to take exams.

A. By the time I’ve taken my exam, I will have started training to be an accountant for a year.

B. By the time I take my exam, I will have been in training to be an accountant for a year.

C. By the time I took my exam, I would have trained to be an accountant for a year.

D. By the time I’ve taken my exam, I will be training for a year.

Question 11. The government knows the extent of the problem. The government needs to take action soon.

A. The government knows the extent of the problem whereas it needs to take action soon.

B. The government knows the extent of the problem so that it needs to take action soon.

C. Knowing the extent of the problem, the government needs to take action soon.

D. The government knows the extent of the problem, or else it needs to take action soon.

Question 12. The substance is very toxic. Protective clothing must be worn at all times.

A. Since the substance is very toxic, so protective clothing must be worn at all times.

B. So toxic is the substance that protective clothing must be worn at all times.

C. The substance is such toxic that protective clothing must be worn at all times.

D. The substance is too toxic to wear protective clothing at all times.

Question 13. I accepted the new job after all. It is making me feel exhausted.

A. Perhaps I shouldn’t have accepted this new job, as it’s making me feel exhausted.

B. Perhaps it would have been better if I hadn’t agreed to this new job since it is so boring.

C. It is of deep regret that I didn’t turn down the job offer due to its hardship and long hour work.

D. If it had not been for my acceptance the new job offer, I wouldn’t have felt exhausted.

Question 14. Since 1970, the United Nations has been celebrating April 22nd as Earth Day. It attracts millions of people worldwide to join in to promote public awareness of environmental protection.

A. Since 1970, the UNs has been celebrating April 22nd as Earth Day because it attracts millions of people worldwide to join in to promote public awareness of environmental protection.

B. The UNs has been celebrating April 22nd as Earth Day, which millions of people worldwide are attracted to join in it to promote public awareness of environmental protection.

C. Since 1970, the UNs has been celebrating April 22nd as Earth Day, which attracts millions of people worldwide to join in to promote public awareness of environmental protection.

D. Since 1970, the UNs has been celebrating April 22nd as Earth Day so that more people join in to promote public awareness of environmental protection.

Question 15. We found the bad weather very inconvenient. We chose to find a place for the night.

A. The bad weather prevented us from driving any further.

B. Bad weather was approaching, so we started to look for a place to stay.

C. Seeing that the bad weather had set in, we decided to find somewhere to spend the night.

D. Because the climate was so severe, we were worried about what we’d do at night.

Question 16. He held the rope with one hand. He stretched it out.

A. The rope is held with one hand then he stretched it out.

B. Stretching the rope out, he holds it with one hand.

C. Holding the rope with one hand, he stretched it out.

D. He stretched the rope with one hand and held it.

Question 17. The plan may be ingenious. It will never work in practice.

A. Ingenious as it may be, the plan will never work in practice.

B. Ingenious as may the plan, it will never work in practice.

C. The plan may be too ingenious to work in practice.

D. The plan is as impractical as it is ingenious.

Question 18. I never received the letter. It was sent to the wrong address.

A. Since it was sent to the wrong address, I have never received the letter.

B. I never received the letter because it was sent to the wrong address.

C. I never received the letter because of sending to the wrong address.

D. Sent to wrong address, I never received the letter.

Question 19. In your country, schools are open to all. They accept children of any race, colour or creed.

A. In our country, schools are open to all children irrespective of race, colour or creed.

B. In our country, schools are open to all children except for race, colour or creed.

C. Apart from race, colour or creed, schools are open to all children in your country.

D. Children of any race, colour or creed can be admitted to our schools when they are opened.

Question 20. He felt very tired. He was determined to continue to climb up the mountain.

A. He felt so tired that he was determined to continue to climb up the mountain.

B. Feeling very tired, he was determined to continue to climb up the mountain.

C. Tired as he might, he was determined to continue to climb up the mountain.

D. As a result of his tiredness, he was determined to continue to climb up the mountain.

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Đặng Hải An
13 tháng 4 2021 lúc 21:35

nêu phương pháp phân các dung dịch trong suốt không màu sau:

rượu etylic, dấm ăn 5%, nước vôi trong

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Đỗ Quyên
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💢Sosuke💢
14 tháng 6 2021 lúc 10:55

Câu 1

1) \(A=\sqrt{20}-\sqrt{45}+\sqrt{6+2\sqrt{5}}\)

\(=2\sqrt{5}-3\sqrt{5}+\sqrt{\left(\sqrt{5}\right)^2+2\sqrt{5}+1}\)

\(=-\sqrt{5}+\sqrt{\left(\sqrt{5}+1\right)^2}\)

\(=-\sqrt{5}+\sqrt{5}+1\)

\(=1\)

2) ĐKXĐ: \(x>0;x\ne1\)

\(B=\left(\dfrac{1}{x-\sqrt{x}}+\dfrac{1}{\sqrt{x}-1}\right):\dfrac{\sqrt{x}+1}{\left(\sqrt{x}-1\right)^2}\)

\(=\left(\dfrac{1}{\sqrt{x}\left(\sqrt{x}-1\right)}+\dfrac{1}{\sqrt{x}-1}\right).\dfrac{\left(\sqrt{x}-1\right)^2}{\sqrt{x}+1}\)

\(=\dfrac{1+\sqrt{x}}{\sqrt{x}\left(\sqrt{x}-1\right)}.\dfrac{\left(\sqrt{x}-1\right)^2}{\sqrt{x}+1}\)

\(=\dfrac{\sqrt{x}-1}{\sqrt{x}}\)

\(\Rightarrow B=\dfrac{\sqrt{x}-1}{\sqrt{x}}=\dfrac{1}{2}\)

\(\Leftrightarrow2\left(\sqrt{x}-1\right)=\sqrt{x}\)

\(\Leftrightarrow2\sqrt{x}-2=\sqrt{x}\)

\(\Leftrightarrow2\sqrt{x}-\sqrt{x}=2\)

\(\Leftrightarrow\sqrt{x}=2\)

\(\Rightarrow x=4\left(tmđk\right)\)

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✿✿❑ĐạT̐®ŋɢย❐✿✿
14 tháng 6 2021 lúc 11:01

Câu 5 :

Ta có : \(6a+3b+2c=abc\) \(\Rightarrow\dfrac{6}{bc}+\dfrac{3}{ac}+\dfrac{2}{ab}=1\)

Đặt : \(\left\{{}\begin{matrix}\dfrac{1}{a}=x\\\dfrac{2}{b}=y\\\dfrac{3}{c}=z\end{matrix}\right.\) với \(x,y,z>0\) \(\Rightarrow xy+yz+zx=1\)

Ta biến đổi : \(\dfrac{1}{\sqrt{a^2+1}}=\sqrt{\dfrac{\dfrac{1}{a^2}}{1+\dfrac{1}{a^2}}}=\sqrt{\dfrac{x^2}{1+x^2}}=\sqrt{\dfrac{x^2}{xy+xz+yz+x^2}}=\sqrt{\dfrac{x^2}{\left(x+y\right)\left(x+z\right)}}\)

Chứng minh tương tự ta có :

\(\dfrac{1}{\sqrt{b^2+4}}=\sqrt{\dfrac{y^2}{\left(y+z\right)\left(y+x\right)}}\) ; \(\dfrac{1}{\sqrt{c^2+9}}=\sqrt{\dfrac{z^2}{\left(z+x\right)\left(z+y\right)}}\)

Do đó : \(Q=\sqrt{\dfrac{x^2}{\left(x+z\right)\left(x+y\right)}}+\sqrt{\dfrac{y^2}{\left(y+z\right)\left(y+x\right)}}+\sqrt{\dfrac{z^2}{\left(z+x\right)\left(z+y\right)}}\)

Áp dụng BĐT Cô - si ta được :

\(Q=\sqrt{\dfrac{x^2}{\left(x+z\right)\left(x+y\right)}}+\sqrt{\dfrac{y^2}{\left(y+z\right)\left(y+x\right)}}+\sqrt{\dfrac{z^2}{\left(z+x\right)\left(z+y\right)}}\)

\(\le\dfrac{1}{2}\left(\dfrac{x}{x+z}+\dfrac{x}{x+y}+\dfrac{y}{y+z}+\dfrac{y}{y+x}+\dfrac{z}{z+x}+\dfrac{z}{z+y}\right)\)

\(=\dfrac{1}{2}\left(\dfrac{x+z}{x+z}+\dfrac{x+y}{x+y}+\dfrac{z+y}{z+y}\right)=\dfrac{1}{2}\cdot3=\dfrac{3}{2}\)

Dấu "=" xảy ra khi \(\left\{{}\begin{matrix}a=\sqrt{3}\\b=2\sqrt{3}\\c=3\sqrt{3}\end{matrix}\right.\)

Vậy Max \(P=\dfrac{3}{2}\) khi \(\left\{{}\begin{matrix}a=\sqrt{3}\\b=2\sqrt{3}\\c=3\sqrt{3}\end{matrix}\right.\)

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💢Sosuke💢
14 tháng 6 2021 lúc 11:08

Câu 2

1) Phương trình \(x^2-6x+5=0\) có:

\(a+b+c=1-6+5=0\)

\(\Rightarrow\) Phương trình có hai nghiệm phân biệt \(x_1=1\) và \(x_2=\dfrac{c}{a}=5\)

2) \(\left\{{}\begin{matrix}2\left(x+2\right)=3\left(y-1\right)\\3x+y=6\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2x+4=3y-3\\3x+y=6\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}2x-3y=-7\\3x+y=6\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}2x-3y=-7\\9x+3y=18\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}11x=11\\3x+y=6\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=1\\3+y=6\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=1\\y=3\end{matrix}\right.\)

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Laville Venom
17 tháng 5 2021 lúc 14:14

wow em đang có ý định nè mà tiếng việt hay anh vậy cô

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( •_•)>⌐■-■(☞゚ヮ゚)☞
17 tháng 5 2021 lúc 14:15

Em xin chúc tất cả các anh chị thi cuối kì, thi vào 10, thi tốt nghiệp THPT,...sẽ thật bình tĩnh, kết quả cao,...

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Yeutoanhoc
17 tháng 5 2021 lúc 14:15

Cảm ơn cô nhiều ạ :o

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