2. The man is believed to have been killed by terrorists.

3. The company is thought to be planning a new advertising campaign.

4. The President was reported to have suffered a heart attack.

5. The man is alleged to have been driving at 110 miles an hour.

6. The expedition is known to have reached the South Pole in May.

7. There is said to be a secret tunnel between them.

8. She is considered to have been the best singer that Australia has ever produced.

9. The weather is expected to be good tomorrow.

10. The Prime Minister and his wife are believed to have separated.

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Câu hỏi của Trần Lê Nguyên Mạnh - Toán lớp 9 - Học trực tuyến OLM

Đề phải là số thực không âm mới đúng

Ta có:

\(P=\frac{1}{x^2+2y+3}+\frac{1}{y^2+2z+3}+\frac{1}{z^2+2x+3}\)

\(\le\frac{1}{2}\left(\frac{1}{x+y+1}+\frac{1}{y+z+1}+\frac{1}{z+x+1}\right)\)

Đặt \(x=a^3;y=b^3;z=c^3\)

\(\Rightarrow abc=1\)

Từ đây ta có:

\(2P\le\frac{1}{a^3+b^3+1}+\frac{1}{b^3+c^3+1}+\frac{1}{c^3+a^3+1}\)

\(=\frac{1}{\left(a+b\right)\left(a^2-ab+b^2\right)+1}+\frac{1}{\left(b+c\right)\left(b^2-bc+c^2\right)+1}+\frac{1}{\left(c+a\right)\left(c^2-ca+a^2\right)+1}\)

\(\le\frac{1}{\left(a+b\right)ab+1}+\frac{1}{\left(b+c\right)bc+1}+\frac{1}{\left(c+a\right)ac+1}\)

\(=\frac{c}{a+b+c}+\frac{a}{a+b+c}+\frac{b}{a+b+c}=1\)

Vậy \(P\le\frac{1}{2}\)

mình nghĩ đề sai vì hôm kia đến h nghĩ mãi không ra D:

1, Tom and Mark hope to go skiing in the mountains this weekend if the weather is fine

2, Each of the students in the class has to type their owns report

3, We are really fed up with the television programs today

4, We thought he was planning to go on vacation after the first of the month

1 go => to go

2 own=>owns

3 at  => with

4 is=> was 

tk nha

\(\hept{\begin{cases}\left|xy-4\right|=8-y^2\left(1\right)\\xy=2+x^2\left(2\right)\end{cases}}\)

Ta có: \(\left|xy-4\right|\ge0\left(\forall x,y\right)\)

\(\Rightarrow8-y^2\ge0\left(\forall y\right)\Leftrightarrow y^2\le8\)  (3)

Pt (2) có nghiệm \(\Leftrightarrow\Delta\ge0\)

pt (2) \(\Leftrightarrow x^2-\text{yx}+2=0\)

\(\Delta=y^2-8\ge0\Leftrightarrow y^2\ge8\)   (4)

Từ (3) và (4) \(\Rightarrow y^2=8\Leftrightarrow y=\pm2\sqrt{2}\)

Vậy hpt có nghiệm: \(\hept{\begin{cases}x=\sqrt{2}\\y=2\sqrt{2}\end{cases};\hept{\begin{cases}x=-\sqrt{2}\\y=-2\sqrt{2}\end{cases}}}\)

Gọi vận tốc ô tô đi từ A là x(x>20)

Vận tốc ô tô đi từ B là y(0<y<x)

Vì vận tốc ô tô đi từ A lớn hơn vận tốc ô tô đi từ B là 20km/h nên ta có phương trình: x−y=20(1)

Đổi: 11h30p=1,5h

Sau 1,5h ô tô đi từ A đi được: 1,5x (km)

Sau 1,5h ô tô đi từ B đi được: 1,5 y (km)

Sau 1,5h 2 xe gặp nhau có nghĩa là cả 2 xe đã đi hết đoạn đường AB nên ta có phương trình: 

1,5x+1,5y=150 →x+y=100,

Từ (1), (2) ta có hệ phương trình:

{x−y=20x+y=100⇔{x=60y=40(thoả mãn)

Vậy vận tốc ô tô đi từ A là 60km/h, vận tốc ô tô đi từ B là 40km/h

hình 2

_ I see a man is holding a child and a woman is going to work.

_I can see that in the future, men will take care of children, cook rice, ... and women will be the backbone of the family to make money to feed everyone in the house. But today, in complete contrast, men are the breadwinner of the family, and women stay home to take care of their babies, and cook housework.

_I think this transition is not very appropriate for men, which are healthier than women, so they will do heavy work. Women are weaker than men, so they will do light work such as taking care of children , cooking rice , doing housework

hình 2