a: \(Q=\dfrac{\left(\sqrt{x}+1\right)\left(\sqrt{x}+2\right)-2\sqrt{x}\left(\sqrt{x}-2\right)-5\sqrt{x}-2}{x-4}:\dfrac{\sqrt{x}\left(3-\sqrt{x}\right)}{\left(\sqrt{x}+2\right)^2}\)

\(=\dfrac{x+3\sqrt{x}+2-2x+4\sqrt{x}-5\sqrt{x}-2}{x-4}\cdot\dfrac{\left(\sqrt{x}+2\right)^2}{\sqrt{x}\left(3-\sqrt{x}\right)}\)

\(=\dfrac{-x+2\sqrt{x}}{\sqrt{x}-2}\cdot\dfrac{\sqrt{x}+2}{\sqrt{x}\left(3-\sqrt{x}\right)}\)

\(=\dfrac{-\sqrt{x}\left(\sqrt{x}-2\right)}{\sqrt{x}\left(\sqrt{x}-2\right)\cdot\left(-1\right)}\cdot\dfrac{\sqrt{x}+2}{\sqrt{x}-3}=\dfrac{\sqrt{x}+2}{\sqrt{x}-3}\)

b: Khi x=4-2căn 3 thì \(Q=\dfrac{\sqrt{3}-1+2}{\sqrt{3}-1-3}=\dfrac{\sqrt{3}+1}{\sqrt{3}-4}=\dfrac{-7-5\sqrt{3}}{13}\)

c: Q>1/6

=>Q-1/6>0

=>\(\dfrac{\sqrt{x}+2}{\sqrt{x}-3}-\dfrac{1}{6}>0\)

=>\(\dfrac{6\sqrt{x}+12-\sqrt{x}+3}{6\left(\sqrt{x}-3\right)}>0\)

=>\(\dfrac{5\sqrt{x}+9}{6\left(\sqrt{x}-3\right)}>0\)

=>căn x-3>0

=>x>9

..........unable to sing

........have your father worked in that factory

......driven for two months

..........we try to save our sources of energy, they will soon end

Viết lại câu:

I have learn English for three years.

Viết lại: I started..............

=> I started learning / to learn English three years ago

I started English three year ago

I started learning English three years ago.

4,he didn't work hard ,so he earried a little money.

=> Because of working hard, he earried a little money

5,it started raining heavily an hour ago.

=> It  has rained heavily for an hour

1: we started living here fifteen years ago .

-> we have ...lift here for fifteen years...........................................

2: the last time she visited me was five years ago.

-> she hasn't ..visited me for five years........................................

3: we haven't visited  my grandfather for two months .

-> the last time ....we visited my grandfather was two months ago...................................

4 : i have studied English for three years .

-> i began ....study English three years ago............................................

1: we started living here fifteen years ago .

-> we have .lived here fifteen years ago ..............................................

2: the last time she visited me was five years ago.

-> she hasn't ...visited me for five years ago........................................

3: we haven't visited  my grandfather for two months .

-> the last time ...we ...visited  my grandfather was two months ago..................................

4 : i have studied English for three years .

-> i began ....studying English  three years ago .............................................

81 were

82 haven't understood

83 visited

84 was listening

85 making

Mk làm ở bài cậu đăng lần đầu rrồi đó nha.

~~~~~

học tốt ~

1:this is the first time he has been here.

=>he has...never been here before ............

2,i started playing tennis 3 months ago.

=>i have........played tennis 3 months ago..................

3,they began to plant trees when it stopped raining.

=>they have....planted trees when it stopped raining..................

4,she has never eaten this fruit before.(thấy sai sai)

=> she is.........................

5,it's three days since my uncle left here.

=>my uncle has....left here three days ago .......................

6,the last time i saw him was two weeks ago.

=>i have.........seen him two week ago.......................