BẢO THẦY N guyễn Hàng Minh ý 

The classroom is a place where we play and learn so protecting it is something every student must know. So what do we need to do to keep it clean. First we need to clean, sweep the house, wipe the table cleaning table ..., next we should not throw garbage indiscriminately, but throw it in the trash. Put more trees in the classroom to keep it cool and educate your friends about how to stay clean in class. I criticize some of you for not knowing how to keep your classroom clean. The above actions can help us to protect the environment in which we study in a cool, hygienic way so that we always learn to keep a happy spirit in every class.

 School is a place where we learn, have fun, and have fun. Of course we also have a responsibility to protect and preserve this place. First the simplest thing we need is to not litter the school yard or classroom indiscriminately.After that, all you need to do is propagate to everyone to keep the school clean and beautiful.You can also make suggestions to your teacher or school about the planting of trees and chandeliers in the school yard.Finally, you and the others need to follow the rules, not picking flowers or trees.Let's strive for a green, clean and beautiful school environment!!!

chúc bn hok tốt 

My name is Thảo.  I am in class 7C. I think I can suggest some ways to make my school greener, cleaner and more beautiful. Firstly I will encourage students to go to school by bike or bus. It will be very friendly to the environment. Next, I will talk to teachers at school about putting recycling bins in every classroom. We can reuse or sell the things in these bins. Finally, I will organize the secondhand item exchange festival where students can swap their old items with their friends instead of throwing them away. These activities may not be very big, but they may contribute a good, green part to the environment, precisely here is our school.

2. He asked her where she was going.

3. He asked which way they had gone.

4. I told her to bring it back if it didn't fit.

5. She told us not to try to open it then.

6. I asked her if it was going to be a fine day that day.

7. She said that he was not at home.

8. The girl wanted to know if the bus station was far away.

9. Tom told Ann not to stay out late.

10. He asked her to let him borrow her car.

11. Thomas asked Jean if he had seen his gloves.

12. I told Mary not to leave the window open.

13. She said that she would have a cup of tea with me.

14. She said that she would pay him if she could.

15. She asked what I was going to do the next summer.

\(ĐK:x\in R\\ PT\Leftrightarrow\sqrt{\left(x+\dfrac{1}{2}\right)^2}=7-2x\\ \Leftrightarrow\left|x+\dfrac{1}{2}\right|=7-2x\\ \Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{2}=7-2x,\forall x+\dfrac{1}{2}\ge0\\x+\dfrac{1}{2}=2x-7,\forall x+\dfrac{1}{2}< 0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{13}{6},\forall x\ge-\dfrac{1}{2}\left(tm\right)\\x=\dfrac{15}{2},\forall x< -\dfrac{1}{2}\left(ktm\right)\end{matrix}\right.\Leftrightarrow x=\dfrac{13}{6}\)

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

\(x=\sqrt{9+4\sqrt{5}}-\sqrt{9-4\sqrt{5}}\)

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

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

\(=\sqrt{5}+2-\sqrt{5}+2=4\)

\(y=\sqrt{3+2\sqrt{5}}-\sqrt{3-2\sqrt{5}}\)

Xem lại đề, \(\sqrt{3-2\sqrt{5}}\) không xác định.

\(a,\sqrt{9+4\sqrt{5}}-\sqrt{9-4\sqrt{5}}\\ =\sqrt{\left(2+\sqrt{5}\right)^2}-\sqrt{\left(\sqrt{5}-2\right)^2}\\ =2+\sqrt{5}-\sqrt{5}+2=4\)

Bài 5: 

d: Áp dụng tính chất của dãy tỉ số bằng nhau, ta được:

\(\dfrac{x}{2}=\dfrac{y}{3}=\dfrac{z}{4}=\dfrac{x+y-z}{2+3-4}=\dfrac{-20}{1}=-20\)

Do đó: x=-40; y=-60; z=-80