dễ thì mới dễ xuyên qua chứ

khoong bieet

ko hiểu

Từ bất đẳng thức Cô si ta có:

\(4\left(ab+bc+ca\right)\left(\frac{1}{a^2}+\frac{1}{b^2}+\frac{1}{c^2}\right)\le\left[\frac{ab+bc+ca}{ca}+ca\left(\frac{1}{a^2}+\frac{1}{b^2}+\frac{1}{c^2}\right)\right]^2\)

\(\Rightarrow\)Ta cần chứng minh:

\(\frac{ab+bc+ca}{ca}+ca\left(\frac{1}{a^2}+\frac{1}{b^2}+\frac{1}{c^2}\right)\le\frac{a+b}{c}+\frac{b+c}{a}+\frac{c+a}{b}\)

Vì vai trò của a, b, c trong bất đẳng thức như nhau, nên không mất tính tổng quát ta giả sử \(a\ge b\ge c\)nên bất đẳng thức cuối cùng đùng. Vậy bất đẳng thức được chứng minh.

sai r bạn ơi ko biết còn đòi

Có và ko

có và ko

C nhé, vì đây là phương trình tổng quát của vecto pháp tuyến đó, tọa độ a,b của VTPT lần lượt là hệ số của x và y

2,1 nha

dear Army.

That's honored to receive your letter.

You know, sleep is one of the most important activities for human’s body, so you should follow my advice to avoid insomnia and stressful.

First of all, diet is the key. You had better eat the food rich in carbohydrat and avoid low protein foods, such as cheese, milk, soya milk, tofu, nuts, honey, almonds, bananas, whole grains, beans, rice, avocados, sesame seeds, sunflower seeds, or papayas, and do not eat greasy foods, fast foods fried chicken, hamburger, pizza, hot dog,... .Remember don’t eat before sleeping. Additionally, try some tips drinking a glass of warm milk or listening to sooth music. You also need a comfortable dark room with ideal temperature before sleep.

To avoid stress,the most important thing is to stop thinking too much and worrying too much, get rid of sad and annoying happenings all day.

I hope you will be successful, and also get high score at the IELTS examination. Have a great day.

                                                                                                             Expert: Mary 

Our travel brochure is about an eco tour to Central Highlands. The tour leaves the ABC office at 5 a.m. every Saturday and gets back at 8 p.m. the next day. The two-day tour doesn’t cost too much: only VND 900,000 per person. During this trip, you can go biking in the forest and watch wildlife. You can also visit Don village, enjoy cooking and staying overnight with local ethnic families. If we have enough time, we may visit coffee plantations to enjoy fresh coffee. But you need to behave responsibly. You should speak softly while watching the animals. And remember to respect local people's life and not to litter.

Mông cô chấm điểm cho em ạ!Cảm ơn cô.

Chép mạng vừa thôi bạn Mỹ Châu ơi!

https://tech12h.com/de-bai/use-information-about-eco-tours-sa-pa-or-central-highlands-speaking-section-design-travel

Thưa cô đây là link ạ, cô có thể vào thống kê của em để dùng

TH2 có hơi sai sai nhé..

( Đ hiểu kiểu gì mà mấy bạn cứ trả lời TH2, thôi thì mình sửa lại vậy =)) )

TH2 : a = 2 - b => a² = b² - 4b + 4. Thay vào (**) ta có :

a² - b² = 2x <=> - 4b + 4 = 2x

<=> - 2b = x - 2

<=> 4b² = x² - 4x + 4

<=> 4 - 4x = x² - 4x + 4

<=> x² - 4x + 4 + 4x - 4 = 0

<=> x² = 0 <=> x = 0 (tmđk)

Vậy pt có tập nghiệm S = { - 3/5 ; 0 }

WATER

Save water

Do not litter in rivers and lakes

Take advantage of clean water

Companies do not discharge chemicals into rivers, lakes and seas

CHÚC BẠN HT 

Forests play an important part of life on earth. They absorb Co2 and harmful gases produced during burning fossil fuels, which reduce air pollution, heat, flood and other disasters. They are also home of a wide variety of fauna and floral.

Nontheless, nowadays, jungles’ area is decreasing because of exploitation of woods and land. So what we can do to stop them from disappearing gradually? First, build plans carefully of land use for public facilities and cultivation. Furthermore, the land that trees were cut down needs to be replaced by new plants and be taken care properly. Last but not least, government must raise awareness on the importance of trees in education, and build tree-growing campaigns across the country.

To sum up, forests must be protected to maintain the life on earth and steps must be taken to prevent further consequences.