Ta có: \(\hept{\begin{cases}\left(\frac{1}{x}+y\right)+\left(\frac{1}{x}-y\right)=\frac{5}{8}\\\left(\frac{1}{x}+y\right)-\left(\frac{1}{x}-y\right)=-\frac{3}{8}\end{cases}\Leftrightarrow\hept{\begin{cases}\frac{2}{x}=\frac{5}{8}\\2y=-\frac{3}{8}\end{cases}\Leftrightarrow}\hept{\begin{cases}x=\frac{16}{5}\\y=-\frac{3}{16}\end{cases}}}\)

\(2x+x+x+83=-2\\\Rightarrow3x+x+83=-2\\\Rightarrow4x+83=-2\\\Rightarrow4x=-2-83\\\Rightarrow4x=-85\\\Rightarrow x=\dfrac{-85}{4}\)

2x + x + x + 83 = -2

(2x + 2x) + 83 = -2

4x + 83 = -2

4x = (-2) - 83

4x = -85

x = -21,25

Câu này mình chưa học đến mình mới lớp 5 thôi đây toán lớp 7 chưa có ai chả lời được

Answer:

Câu 1:

\(5x+7y=40\)

\(\Rightarrow\hept{\begin{cases}5x=40\\7y=40\end{cases}}\Rightarrow\hept{\begin{cases}x=40:5\\y=40:7\end{cases}}\Rightarrow\hept{\begin{cases}x=8\\y=\frac{40}{7}\end{cases}}\)

Câu 2:

\(P=\frac{2x-5}{x+2}\left(x\ne-2\right)\)

\(=\frac{2x+4-9}{x+2}\)

\(=\frac{2x+4}{x+2}-\frac{9}{x+2}\)

\(=\frac{2\left(x+2\right)}{x+2}-\frac{9}{x+2}\)

\(=2-\frac{9}{x+2}\)

Mà để cho \(P\inℤ\) thì \(\frac{9}{x+2}\inℤ\)

\(\Rightarrow9⋮\left(x+2\right)\)

\(\Rightarrow x+2\inƯ\left(9\right)=\left\{\pm1;\pm3;\pm9\right\}\)

Có bảng sau:

Vậy \(x\in\left\{-11;-5;-3;-1;1;7\right\}\) thì \(P\inℤ\)

a) Ta có: 2|x + 2| \(\ge\)0 \(\forall\)x

=> 2|x + 2| + 15 \(\ge\)15 \(\forall\)x

Hay A \(\ge\)15 \(\forall\)x

Dấu "=" xảy ra <=>x + 2 = 0 <=> x = -2

Vậy Min A = 15 tại x = -2

b) Ta có: 2(x + 5)⁴ \(\ge\)0 \(\forall\)x

         3|x + y + 2| \(\ge\)0 \(\forall\)x;y

=> 20 - 2(x + 5)⁴ - 3|x + y + 2| \(\le\)20 \(\forall\)x;y

Hay B \(\le\)20 \(\forall\)x;y

Dấu "=" xảy ra <=> \(\hept{\begin{cases}x+5=0\\x+y+2=0\end{cases}}\) <=> \(\hept{\begin{cases}x=-5\\y=-2-x\end{cases}}\) <=> \(\hept{\begin{cases}x=-5\\y=-2-\left(-5\right)=3\end{cases}}\)

Vậy Max B = 20 tại x = -5 và y = 3

1 He has visited Ha Noi for 10 years

2 London is the biggest city in the world

3 Mai likes playing football because it is so funny

4 The winner will be .....

1. He has visited Hanoi for ten years.

2. London is the biggest city in the world.

3. Mai likes playing football because it is so funny.

4. ha là gì?????????

1. She has visited HN for 10 years

2. London is the biggest city in the world

3. Mai likes playing football because it is so funny

4. Ha will be the winner

1. I have seen it

2. He has left to Hanoi since 2018

3. I have not eaten banana

4. She has learned English for 4 years.

5. I have study Math since 2010

I have finished my homework

She hasn't read this book yet.

He has written a letter to his brother

They have been to Paris

Mai hasn't eaten this food before

This is the first time I have read this book

Bạn dựa vào cấu trúc mà đặt câu tiếp nhá

I have seen that movie twenty times.

I think I have met him once before.There have been many earthquakes in California.

People have traveled to the Moon.People have not traveled to Mars.

Have you read the book yet?

Nobody has ever climbed that mountain.

Has there ever been a war in the United States?

Yes, there has been a war in the United States.

I have been to France.I have been to France three times.

I have never been to France.

I think I have seen that movie before.

He has never traveled by train.

Joan has studied two foreign languages.

Have you ever met him?

No, I have not met him.

You have grown since the last time I saw you.

The government has become more interested in arts education.

Japanese has become one of the most popular courses at the university since the Asian studies program was established.