Ta có:

\(xy+2x+y+11=0\\ \Rightarrow xy+2x+y+11+2=0+2\\ \Rightarrow x\left(y+2\right)+y+2=2-11\\ \Rightarrow\left(y+2\right)\left(x+1\right)=-9\)

\(\Rightarrow\left(y+2\right)\left(x+1\right)=1.-9\) hoặc \(\left(y+2\right)\left(x+1\right)=-1.9\)

TH1: \(y+2=1;x+1=-9\)

\(y+2=1\Rightarrow y=1-2\\\Rightarrow y=-1\)

\(x+1=-9\Rightarrow x=-9-1\\ \Rightarrow x=-10\)

TH2: \(y+2=-9;x+1=1\)

\(y+2=-9\Rightarrow y=-9-2\\ \Rightarrow y=-11\)

\(x+1=1\Rightarrow x=1-1\\ \Rightarrow x=0\)

TH3: \(y+2=-1;x+1=9\)

\(y+2=-1\Rightarrow y=-1-2\\ \Rightarrow y=-3\)

\(x+1=9\Rightarrow x=9-1\\ \Rightarrow x=8\)

TH4: \(y+2=9;x+1=-1\)

\(y+2=9\Rightarrow y=9-2\\ \Rightarrow y=7\)

\(x+1=-1\Rightarrow x=-1-1\\ \Rightarrow x=-2\)

Vậy: \(\left(x;y\right)\in\left\{\left(-10;-1\right);\left(0;-11\right);\left(8;-3\right);\left(-2;7\right)\right\}\)

Ta có:

1) Q(0)=1

\(a.0^2+b.0+c=Q\left(x\right)=1\\ \Rightarrow c=1\)

2) Q(1)=6

\(a.1^2+b.1+c=6\\ \Rightarrow a+b+1=6\\ \Rightarrow a+b=5\)

3) Q(2)=5

\(a.2^2+b.2+c=5\\ \Rightarrow4a+2b+1=5\Rightarrow4a+2b=4\)

Theo lập luận:

\(a+b=6\Rightarrow a=6-b\)

Thay \(a=6-b\) vào biểu thức \(4a+2b=4\), ta có:

\(4\left(6-b\right)+2b=4\\ 24-4b+2b=4\\ 24-2b=4\\ 2b=24-4\\ 2b=20\\ b=20:2\\ \Rightarrow b=10\)

Vậy: \(b=10\)

Theo bài ra:

\(\dfrac{5-x}{-25-y}=\dfrac{x}{y}\\ \Rightarrow\left(5-x\right)y=\left(-25-y\right)x\\ \Rightarrow5y-xy=-25x-xy\\ 5y=-25x-xy+xy\\ 5y=-25x\\ \Rightarrow\dfrac{y}{x}=-\dfrac{25}{5}\\ \Rightarrow\dfrac{y}{x}=-5\)

Vậy: \(\dfrac{y}{x}=-5\)

1.In Viet Nam, one of the most popular activity after school is soccer.

--> In Vietnam, one of the most popular activity after school is soccer.

2. When I see Mai, I think she looks very happily.

--> When I see Mai, I think she looks very happy

3. How do you go to see the dentist? – Once or twice a month.

--> How often do you go to see the dentist? – Once or twice a month.

4. Ba has lots of English books . He will borrow Lan some.

--> Ba doesn't has lots of English books . He will borrow Lan some.

5. You had better not to touch an electrical device with wet hands.

--> You will be better not to touch an electrical device with wet hands.

6. My mom was so angry because I arrived at home late at Christmas Eve last year.

--> My mom was so angry because I arrived home late at Christmas Eve last year.

7. I hope she’ll be a famous actor someday because she’s good at acting.

--> I hope she’ll be a famous actress someday because she’s good at acting.

8. Do you understand how do I feel now?

--> Do you understand how I feel now?

9. Why do children afraid of going to see the dentist?

--> Why children are afraid of going to see the dentist?

10. Are you used to be a waiter at that hotel?

--> Did you used to be a waiter at that hotel?

= 19 jjjjjjjjjjjjjjjjjjjjjjjjjjjjj

Nguyễn Lương Bảo Tiên làm đúng rồi

\(\dfrac{1-1}{1+2}+\dfrac{1-1}{1+2+3}+\dfrac{1-1}{1+2+3+4}+...+\dfrac{1-1}{1+2+3+...+2012}\)

\(=\dfrac{0}{1+2}+\dfrac{0}{1+2+3}+\dfrac{0}{1+2+3+4}+...+\dfrac{0}{1+2+3+4+...+2012}\)

\(=0+0+0+...+0\)

\(=0\)

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Bài này dễ mà bạn. Cơ mà hình như bạn ghi sai đề, sao khúc đầu thì nhân mà khúc cuối lại cộng thế?

1. They are used to going in the rain

2. We used to live in Hue when we were young

3. He gets used to staying up late studying

4. There used to be a paddy field there

5. My mother is used to going shopping

6. Her brothers used to go abroad

Câu hỏi: Tính giá trị của xyz tại z là một số thực sao cho:

x(y+z)=32; y(x+z)=27; z(x+y)=35

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Theo bài ra, ta có:

\(x\left(y+z\right)=32\\ \Rightarrow xy+xz=32\\ \Rightarrow xy=32-xz\)

\(z\left(x+y\right)=35\\ \Rightarrow xz+yz=35\\ \Rightarrow xz=35-yz\)

Thay \(xy=32-xz;xz=35-yz\) vào biểu thức \(xy+xz=35\), ta có:

\(32-xz+35-yz=32\\32+35-xz-yz=32\\ 67-xz-yz=32\\ xz-yz=67-32\\ xz-yz=35\)

Theo lập luận, ta có:

\(xz+yz=35\) và \(xz-yz=35\)

\(\Rightarrow xz=\dfrac{35+35}{2}=\dfrac{70}{2}=35\)

\(\Rightarrow yz=35-xz=35-35=0\)

\(\Rightarrow y=0\) hoặc \(z=0\)

Mà \(z\ne0\left(xz=35\right)\) nên: \(y=0\)

Vì \(y=0\) nên: \(xyz=0\)

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Mình nghĩ vậy, không biết đúng không