Chào em, em tham khảo nhé!

1. We had an excursion to the Lake Hudson => Lake Hudson (chúng ta không dùng the trước tên hồ), a man-made reservoir in Oklahoma last Sunday.

2. Different kinds of newspapers arranged => are arranged (câu bị động) on the shelves when the teacher came into the class.

3. The Great Wall is China's longer => China's longest (câu so sánh hơn nhất) structure.

Chúc em học tốt và có những trải nghiệm tuyệt vời tại olm.vn!

1. We had an excursion to the Lake Hudson, a man-made reservoir in Okalahoma last Sunday .

=> bỏ

2. Different kinds of newpapers arranged  on the shelves when the teacher came into the class .

=> are arranged

3. The Great Wall is China's longer structure .

=> longest 

\(\left(1-a+a^2\right)\left(1-b+b^2\right)=1-b+b^2-a+ab-ab^2+a^2-a^2b+a^2b^2.\)

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

Tương Tự : \(\left(1-c+c^2\right)\left(1-d+d^2\right)\ge\frac{1+c^2d^2}{2}\)

(1-a+a²) (1-b+b²) = 1-b+b²-a+ab-ab²+a²-a²b+a²b².

=2-2a-2b+2b²+2ab+2a²-2ab(a+b)+2a²b^{2                                                                                                                                                                                   =}(a-b)²+1+a²b²+(1-a)²(1-b)²> 1+a²b²                                                                                                                                                                                         2                          2                                                                                                                                                       Tương Tự:(1-c+c²) (1-d+d²) > 1+c2d²                                                                                                                                                                                                                                                         2                                                                                                                                             

Đặt 8t=2x

\(d\left(8t\right)=2dx\Rightarrow\frac{d\left(8t\right)}{2}=dx\)

Đổi cận x=0 t=0       x=8 t=2

a , ta có:AE//CF (vì cùng vuông góc vsBD)

=> góc FCO= góc EAO (vì so le trong )

      OA = OC (theo t/c hình bh )

xét 2 tam giác vuông OAE và OCF có:

           góc FOC = góc EAO ( cm trên )

            OA = OC (cmt)

   =>tg OAE = tg OCF (cạnh huyền - góc nhọn )

   =>OE = OF ( 2 cạnh tương ứng )

 b. ta có : AE// CF ( theo a ) (1)

               AE = CF ( vì tg OAE= tg OCF ( theo a )) (2)

 từ (1) và (2) => AECF là hbh

 ( hi vọng đúng !!)

tam giác ABC vuông tại A có AT là đường cao 

Áp dụng định lí Py ta go ta có : \(AB^2+AC^2=BC^2\Rightarrow25-AB^2=AC^2\)(1) 

* Theo hệ thức : \(\frac{1}{AB^2}+\frac{1}{AC^2}=\frac{1}{AT^2}\Rightarrow\frac{1}{4}=\frac{1}{AB^2}+\frac{1}{25-AB^2}\)( theo 1 ) 

\(\Rightarrow AB=2\sqrt{5};\sqrt{5}\)

TH1 : \(25-\left(2\sqrt{5}\right)^2=AC\Rightarrow AC=\sqrt{5}\)

TH2 : \(25-\left(\sqrt{5}\right)^2=AC\Rightarrow AC=2\sqrt{5}\)

Gọi BH là z ( z>0), thì HC là 5-z

ΔABC vuông tại A có:

AH.BC=BH.HC (định lý 3)

⇔ 2² = z(5-z)

⇔ z² - 5z + 4 = 0

⇔ z(z-1) - 4(z-1) = 0

⇔(z-4)(z-1)=0

⇔\(\left[{}\begin{matrix}z-4=0\\z-1=0\end{matrix}\right.\)

⇔\(\left[{}\begin{matrix}z=4\left(nhận\right)\\z=1\left(nhận\right)\end{matrix}\right.\)

TH1:Nếu z=4

ΔABC vuông tại A có:

x²=BC.BH ( định lý 1)

⇔ x²= 5.4

⇔ x²= 20

⇒x=\(2\sqrt{5}\)

ta có: y²= BC.HC ( định lý 1)

Chứng minh tương tự như trên ta được

y= \(\sqrt{5}\)

TH2: Nếu z=1

Chứng minh tương tự như TH1 ta được:

x=\(\sqrt{5}\)

y= \(2\sqrt{5}\)

1. Tam Coc - Bich Dong, which belongs to Trang An Scenic Landscape Complex, is well known for its poe and inspirational natural scenery.

2. It is the second nicest cavern in Viet Nam, after Huong rich Cavern.

3. Bich Dong Pagoda was built in Le Dynasty in Bich Dong Cavern which/whose name means “Green Pearl Cavern”.

4. Tam Coc Cavern consists of Ca cave, Hai cave and Ba cave, all of which offer both beauty and mystery to tourists.

5. Visiting Tam Coc Cavern, tourists will feel  getting lost in such a hidden fairy site.

6. In brief, it is an ideal ecological spot for lovers of nature.

,mkjh

1. Progress in science is being made day after day. → People are making progress in science day after day.

2. A French architect designed the palace.

3. They have paved the road in front of my house.

4. You can see that they haven't washed the dishes.

5. They will not increase our salaries this year.

6. Didn't they build that theatre two years ago?

7. They may discuss the problem again.

8. They have offered my brother a well – paid job.

9. People reported that the war started again in South American.

10. He told me that his football team had played well last season.

2. A French architect designed the palace.

3. They have paved the road in front of my house.

4. You can see that they haven't washed the dishes.

5. They will not increase our salaries this year.

6. Didn't they build that theatre two years ago?

7. They may discuss the problem again.

8. They have offered my brother a well – paid job.

9. People reported that the war started again in South American.

10. He told me that his football team had played well last season.

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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