Join the pairs of sentences together.Use Because,as,since

1)He is playing the piano very softly.He doesn't want to disturb anyone

2)He took off his shoes.He didn't want to make any noise

3)She doesn't let her son play with scissors.He may cut himself

4)They talked in whispers.They didn't want anyone to overhear them

5)He is learning very hard.He wants to pass the entrance exams

6)Don't put on any more coal.The chimney may catch fire

7)My mother has packed the vase carefully.She is afraid that it gets broken in the post

Join the pairs of sentences together.Use because,As,Since.

1)He rushed into the burning house.He wanted to save the child

2He fixed a metal ladder to the wall below his window.He wanted to be able to escape if there was a fire

3)She is putting nets over her strawberry plants.She doesn't want the birds to eat all her strawwberries

Dẫn từ từ 16,8l khí CO2(đktc) vào 600ml dung dịch Ca(OH)2 1M.Tính khối lượng kết tủa thu được

Giải hệ phương trình:

a)\(\left\{{}\begin{matrix}\dfrac{3x+2}{x-1}-\dfrac{3y-1}{y+2}=0\\\dfrac{2}{x-1}+\dfrac{3}{y+2}=1\end{matrix}\right.\)

b)\(\left\{{}\begin{matrix}\dfrac{4x-5}{x+1}+\dfrac{2y-3}{y-5}=8\\\dfrac{3}{x+1}-\dfrac{2}{y-5}=-1\end{matrix}\right.\)

c)\(\left\{{}\begin{matrix}\dfrac{x+y-2}{x+1}+\dfrac{3-x}{y+1}=\dfrac{5}{4}\\\dfrac{3\left(x+y-2\right)}{x+1}-\dfrac{5-x+2y}{y+1}=\dfrac{3}{4}\end{matrix}\right.\)

d)\(\left\{{}\begin{matrix}\dfrac{x-y+1}{x-3}+\dfrac{x+1}{y-3}=\dfrac{-7}{2}\\\dfrac{2\left(x-y+1\right)}{x-3}-\dfrac{x+y-2}{y-3}=-\dfrac{9}{2}\end{matrix}\right.\)

e)\(\left\{{}\begin{matrix}x^2-y^2+2y=1\\\left(x+y\right)^2-2x-2y=0\end{matrix}\right.\)

f)\(\left\{{}\begin{matrix}4x^2+y^2-4xy=4\\x^2+y^2-2\left(xy+8\right)=0\end{matrix}\right.\)

Giải hệ phương trình

a)\(\left\{{}\begin{matrix}\dfrac{2x-1}{x+2}-\dfrac{5}{y-1}=-\dfrac{14}{3}\\\dfrac{3}{x+2}+\dfrac{\left(2y+3\right)}{y-1}=8\end{matrix}\right.\)

b)\(\left\{{}\begin{matrix}\dfrac{2x}{1-x}+\dfrac{3}{y+2}=-\dfrac{2}{5}\\\dfrac{5}{1-x}-\dfrac{4y}{y+2}=\dfrac{1}{10}\end{matrix}\right.\)

chuyển sang bị động:

1.They think that this book is no use

2.People believe that he was injured in the accident

3.They say many people are homeless after the floods

4.We believe that he is staying painting in America

5.People think that he knows English well (chuyển theo 2 cách)