\(x^2+x+3=y^2\)

\(\Leftrightarrow4x^2+4x+12=4y^2\)

\(\Leftrightarrow\left(2x+1\right)^2-4y^2=-11\)

\(\Leftrightarrow\left(2x+1-2y\right)\left(2x+1+2y\right)=-11\)

Lập bảng ra

\(x^2+x+\left(3-y^2\right)=0\)

Xét \(\Delta=1^2-4\left(3-y^2\right)\ge0\Leftrightarrow4y^2-11\ge0\)

Ta cần có \(4y^2-11=k^2\Leftrightarrow\left(2y\right)^2-k^2=11\Leftrightarrow\left(2y-k\right)\left(2y+k\right)=11\)

Lập bảng tìm y thay vào tìm x.

các bạn ơi giải bài này đi mình cần gấp ai giả được minh cho 1 thích nhé

Help me!!!

Gọi quãng đường AB là x ( x>0)

Thời gian người đó đi từ A đến B là \(\frac{x}{30}\)( h )

Thời gian người đó đi từ B về A  là \(\frac{x}{24}\)( h )

Thời gian người đó làm việc là 1( h )

Tổng thời gian người đó đi là \(\frac{11}{2}\)( h )

Theo bài ra ta có

\(\frac{x}{30}+1+\frac{x}{24}=\frac{11}{2}\)

\(\frac{x}{30}+\frac{x}{24}=\frac{11}{2}-1\)

\(\frac{x}{30}+\frac{x}{24}=\frac{9}{2}\)

\(\frac{4x+5x}{120}=\frac{540}{120}\)

9x=540

x=540:9

x=60 km

Vậy quãng đường AB là 60 km

1+1=2 nhé<3

= 2 

k mình nhé

Chia tam giác đó thành 16 tam giác đều bằng nhau cạnh 1/4. Theo Dirichlet tồn tại 2 điểm cùng thuộc 1 tam giác và khoảng cách giữa chúng không lớn hơn 1/4 .

\(\Leftrightarrow8\left(x+\frac{1}{x}\right)^2+4\left(x^2+\frac{1}{x^2}\right)\left[\left(x^2+\frac{1}{x^2}\right)-\left(x+\frac{1}{x}\right)^2\right]=\left(x+4\right)^2.ĐKXĐ:x\ne0\)

\(\Leftrightarrow8\left(x+\frac{1}{x}\right)^2+4\left(x^2+\frac{1}{x^2}\right)\left(x^2+\frac{1}{x^2}-x^2-2-\frac{1}{x^2}\right)=\left(x+4\right)^2\)

\(\Leftrightarrow8\left(x+\frac{1}{x}\right)^2-8\left(x^2+\frac{1}{x^2}\right)=\left(x+4\right)^2\)

\(\Leftrightarrow8\left[\left(x+\frac{1}{x}\right)^2-\left(x^2+\frac{1}{x^2}\right)\right]=\left(x+4\right)^2\)

\(\Leftrightarrow8\left(x^2+2+\frac{1}{x^2}-x^2+\frac{1}{x^2}\right)=\left(x+4\right)^2\)

\(\Leftrightarrow16=\left(x+4\right)^2\)

\(\Leftrightarrow x^2+8x+16=16\)

\(\Leftrightarrow x^2+8x=0\)

\(\Leftrightarrow x\left(x+8\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x=0\left(l\right)\\x=-8\left(n\right)\end{cases}}\)

V...\(S=\left\{-8\right\}\)

^^

bạn ghi sai đề ở chỗ \(\left(x+\frac{1}{x}\right)^2\)chứ ko phải \(\left(x+\frac{1}{x^2}\right)^2\)nhé

Nowadays, more and more people choose to live in the city. In this essay, I will discuss about the advantages and disadvantages of living in the city.

It can't be denied that living in the city has many benefits. First of all, if we live in the city, we will have many chances get the developing science and technology. It means that we will have more job opportunities and broaden our knowledge more easily. Secondly, we will have many different ways to spend our free time. There are a lot of theatres, concerts and other kinds of entertainment. There is always a lot to do and visit There are a lot of possibilities of shopping. In various shopping centres and galleries you can buy whatever you want. What is more, a big city is a potential market for trading activities, so we can earn more money to provide our family a comfortable life

Besides advantages, living in the city brings to us a lot of disadvantages. Firstly, a problem about which everyone is worrying is environment. The increase of factories based on industrialization and modernization has severely polluted environment. Smoke from factories' chimneys not only pollutes the air but also makes people get many serious cancers. Sewage is bumped into rivers without being purged, which threatens underwater ecosystems. The second drawback of living in the city is society's vices such as drug addiction. Young people. especially the students, are easily spoiled by bad habits. If people use up all the money, they can't control themselves and even become robbers or murders. Moreover, a problem that many people living in the city have is heartlessness. With some people, it's not worth being worried and it has no effect on our life, people are too busy to care for any others. But if more and more people become heartless, the society will be worse, no one cares another one, they live boring lives, every purposes became meaningless, without love, sympathy and many other good things.

There are good things as well as bad thing of living in the city. However, I strongly believed that advantages outweigh disadvantages. If people know how to live and enjoy their life, living in the city is one of the most interesting things that people want to experience.