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?

Are they read books before sleeping?

1. The dentist fills the cavity in my tooth and it stopped hurting right afterwards

2.I don't want to meet Paul so when he went into the room, I leaved

3. My dentist told me eat less sweets

4. People need a pair of rackets to play the game

5. She is meeting her parents now, I don't think see came on time

6. My aunts usually flies to Bangkok and Hong Kong. Next Sunday they fly to Hong Kong

7. Does Mai wash her hands before have meals?

8. What does your father do? He's a teacher but he not working at the moment.

9. My sister swims badly. She should practice swims more

10, They will get used to living in the USA

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

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

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

\(=0\)

---

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

---

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: \(xyz=0\)

---

Mình nghĩ vậy, không biết đúng không