Mong cô duyệt bái cho em ạ !

I am Kim Lee. I am now 17 years old. When I was at the age of 15 I started getting acne.

My face looked terrible and I always felt depressed and insecure about appearance. Then I came to see one of my best friends, who always gave me good advice and asked her for advice. She told me that I should wash my face several times a day and try different anti­acne products, squeeze pimples often. But this way doesn't help a lot. The result of that was 60% of my face was covered with acne.

I found a website advertising an effective way to remove acne, and they advised me to see Dr Kangnam. Dr Kangnam gave me a detailed plan to remove acne on my face. First, he advised me to wash my face only twice a day because washing face too often may cause skin irritation. Second, I have to take prescription medicine. Third, I had to follow a healthy diet. Dr Kangnam also advised me not to stay up late. After six months acne clears up. And now I feel very happy and confident.

I am Kim Lee. I am now 17 years old. When I was at the age of 15 I started getting acne.

My face looked terrible, I always felt depressed and insecure about appearance. Then I came to see one of my best friends, who always gave me good advice. I asked her for some advice. She told me that I should wash my face several times a day and try different anti­acne products, squeeze pimples often. But this way didn’t help a lot. The result was that 60% of my face was covered with acne.

I found a website advertising an effective way to remove acne, and they advised me to see Dr Kangnam. Dr Kangnam gave me a detailed plan to remove acne on my face. First, he required me to wash my face only twice a day because washing face too often may cause skin irritation. Second, I had to take prescription medicine. Third, I was told to follow a healthy diet, including enough nutrients, eating lots of vegetables, drinking 2 litter of water every day and not consuming too much spicy hot food. Dr Kangnam also said that I shouldn’t stay up late, sleep at least 6 hours a day if I wanted my face to be smooth. After six months of following his instruction, acne clears up amazingly, my skin is smoother and I feel so happy and confident.

Dear Anne(Hà Lam).

I received your email last week, in which you asked me about my city New York in 2050. There are different ideas about this question. I thought it in a few days, and now I can give you two predictions.

Let's take a look at an optimis viewpoint. In 2050 New York will become a more liveable city than ever before for lots of reasons. The city authorities have built a very careful plan to promote self-driving electric taxis to deal with crowded public transport. In addition, the city dwellers are encouraged to use city's building roofs for gardens fertilised with compose in order to recycle rubbish and reduce pollution. The government will also build offshore windfarms to replace ageing electricity network.

On the other hand, pessimis people think that the city life won't be a safe place to live in because the government cannot control the use of guns, and therefore the crime rate will be higher. People's life will also continue to be threatened because of natural disasters such as floods, storms, earthquakes. The effects of global warming have great impacts on the city dwellers.

That's all about my answer to your question. I hope you will be satisfied with it, Nam.

Best wishes,

Wonie(Quyên)

tham khảo ạ

Dear Bich

Your last email asked me about my city Ha Noi in 2050. Well, but I'm busy and have no time to reply you soon. Today I am writing to you about that question. There are different ideas about this question. I thought about it in a few days, and now I can give you some predictions.

Let's take a look at optimis aspects. In 2050 Ha Noi will become a more modern city for lots of reasons. High technology has been applied in our lives. The robots will replace us for many jobs such as manufacturing, farming, etc. Smart cars which will be commonly used in the road. They will help human beings to decrease the accidents as well as traffic jams.

On the contrary, pessimis people think that the city life will be a dangerous place to live in because the environment is completely polluted. The effects of global warming have great impacts on the city dwellers, higher temperature in the summer and colder climate in the winter. There are a lot of means of transport so that emission from them cause air pollution. Our health will be threatened because of low air quality index.

That's all about my thoughts about your question. I hope you will be satisfied with it, Bich.

Best wishes,

Chau

Dear Peter

I received your email last week, in which you asked me about my city Ha Noi in 2050. There are different ideas about this question. I thought about it in a few days, and now I can give you two predictions.

Let's take a look at optimis aspects. In 2050 Ha Noi will become a more liveable city for lots of reasons. The city authorities have built a very careful plan to promote advanced technology to make greener motorbikes to deal with air pollution. In addition, the city dwellers are encouraged to make use of public transport system to reduce traffic jam. The government will also grow more trees and encourage people to use solar panels.

On the contrary, pessimis people think that the city life will be a dangerous place to live in because the government cannot control the use of private cars and motorbikes. Besides, they don’t believe that citizens will use public transports because this system in our city are aging and not upgraded regularly. It also take time to find a bus and go to the destination in spite of very short distance. People's life will also continue to be threatened because of pollution such as air pollution by burning fossil fuels, emission from cars and motorbikes, noise pollution from constructing buildings and sounding of transportations. The effects of global warming have great impacts on the city dwellers, higher temperature in the summer and colder climate in te winter.

That's all about my answer to your question. I hope you will be satisfied with it, Peter.

Best wishes,

Nga

 k mình nha bn CHÚC BN HỌC TỐT

\(f\left(x\right)=-x^3-2x^2+mx-3\)

\(f'\left(x\right)=-3x^2-4x+m\)

\(f'\left(x\right)>0\Leftrightarrow-3x^2-4x+m>0\Leftrightarrow m>3x^2+4x\)(đúng với mọi \(x\in\left(0,1\right)\))

suy ra \(m\ge max\left(3x^2+4x\right)\)với \(x\in\left[0,1\right]\).

Xét hàm \(g\left(x\right)=3x^2+4x\)với \(x\in\left[0,1\right]\).

\(g'\left(x\right)=6x+4\)

\(g'\left(x\right)=0\Leftrightarrow6x+4=0\Leftrightarrow x=-\frac{2}{3}\notin\left[0,1\right]\).

\(g\left(0\right)=0,g\left(1\right)=7\)

suy ra \(g_{max}=7\)

do đó \(m\ge7\).

Mà \(m\)nguyên, \(m\in\left[-2021,2021\right]\)nên có tổng cộng: \(2021-7+1=2015\)giá trị của \(m\)thỏa mãn. 

Trên này ít người học c3 lắm :<

q1.q2>0 nhé bạn 2 cái đẩy nhau => cùng dấu

Dear Liu!

Last time I told you that I had been thinking about pursuing higher education in the UK. I got started to learn the process of applying for a university in London some time ago. Now I have some questions for you. 

First, what is the procedure for applying for a student visa? Of course. I have to submit an application but what other documents are required? How long does it take me to obtain my student visa? It is important to plan time to wait for visa processing because the time between finding out I have been accepted to go and leaving may be very close together. Second, do 1 have to present my financial documents; for example proof of funds, to prove that I am able to pay for my education? And last, do I need to obtain the International Certificate of Vaccination? Is it required that I have certain vaccinations before I go? What are they? After all. can you make me a checklist: what I should bring and what I should leave at home? 

I wish you and your family the best. I look forward to hearing from you soon. 

                                                                                                     Regards, 

                                                                                                     Mai Anh

Mong cô duyệt bài ạ:

Dear Duc Son,

Last time I told you that I had been thinking about pursuing higher education in the UK. I got started to learn the process of applying for a university in London some time ago. Now I have some questions for you.

First, what is the procedure for applying for a student visa? Of course. I have to submit an application but what other documents are required? How long does it take me to obtain my student visa? It is important to plan time to wait for visa processing because the time between finding out I have been accepted to go and leaving may be very close together. Second, do 1 have to present my financial documents; for example proof of funds, to prove that I am able to pay for my education? And last, do I need to obtain the International Certificate of Vaccination? Is it required that I have certain vaccinations before I go? What are they? After all. can you make me a checklist: what I should bring and what I should leave at home?

I wish you and your family the best. I look forward to hearing from you soon.

Regards,

Dang Phong

Giải phương trình cos3xcos3x−sin3xsin2x=2−3√28 

Phương trình đã cho <=> (2sinx + 1).(3cos4x +2sinx -4) = 3 - 4(1- sin^2 x) 
<=> (2sinx + 1)(3cos4x + 2sinx - 4) = 4sin^2 x - 1 
<=> (2sinx + 1).(3cos4x + 2sinx - 4) = (2sinx + 1).(2sinx - 1) 
<=> (2sinx + 1).(3cos4x + 2sinx - 4) - (2sinx + 1).(2sinx - 1) =0
<=> (2sinx + 1)(3cos4x + 2sinx - 4 - 2sinx+ 1) = 0
<=> (2sinx + 1)(3cos4x -3) = 0
<=>  (2sinx + 1)(cos4x - 1) = 0
(Đến đây pt tích dễ rồi tự giải nha)

\(sin^2x=cos^22x+cos^33x\)

\(\Leftrightarrow1-cos^2x=2cos^2x-1+4cos^3x-3cosx\)

\(\Leftrightarrow4cos^3x+3cos^2x-3cosx-2=0\)

\(\Leftrightarrow\left(cosx+1\right)\left(4cos^2-cosx-2\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}cosx=-1\\cosx=\frac{1\pm\sqrt{33}}{8}\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=\pi+k2\pi\\x=\pm arccos\left(\frac{1\pm\sqrt{33}}{8}\right)+k2\pi\end{cases}}\left(k\inℤ\right)\)