1: Xét (O) có

DC là tiếp tuyến

DA là tiếp tuyến

Do đó: DC=DA

Xét (O) có

EC là tiếp tuyến

EB là tiếp tuyến

Do đó: EC=EB

Ta có: DC+EC=DE

nên DE=AC+EB

1) Vì x=25 thỏa mãn ĐKXĐ nên Thay x=25 vào biểu thức \(A=\dfrac{\sqrt{x}-2}{x+1}\), ta được:

\(A=\dfrac{\sqrt{25}-2}{25+1}=\dfrac{5-2}{25+1}=\dfrac{3}{26}\)

Vậy: Khi x=25 thì \(A=\dfrac{3}{26}\)

2) Ta có: \(B=\dfrac{\sqrt{x}-3}{\sqrt{x}+1}+\dfrac{2x+8\sqrt{x}-6}{x-\sqrt{x}-2}\)

\(=\dfrac{\left(\sqrt{x}-3\right)\left(\sqrt{x}-2\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)}+\dfrac{2x+8\sqrt{x}-6}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)}\)

\(=\dfrac{x-5\sqrt{x}+6+2x+8\sqrt{x}-6}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)}\)

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

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

\(=\dfrac{3\sqrt{x}}{\sqrt{x}-2}\)

câu 3 chứ

\(\dfrac{7}{5}+\dfrac{4}{7}-\dfrac{9}{10}=\dfrac{49-20}{35}-\dfrac{9}{10}=\dfrac{19}{35}-\dfrac{9}{10}=\dfrac{190-315}{350}=\dfrac{-125}{350}\)

\(\dfrac{2}{1}+\dfrac{3}{4}\text{×}\dfrac{8}{5}=\dfrac{8+3}{4}\text{×}\dfrac{8}{5}=\dfrac{11\text{×}8}{4\text{×}5}=\dfrac{88}{20}\)

mấy câu kia áp dụng là dc!

I. Write sentences with the cues given

1. Mai / usually / listen / K - pop music / free time.

→ Mai usually listens to K-pop music in her free time.

2. when / I / be / a child / I / enjoy / play / computer games

→ When I was a child, I enjoyed playing computer games.

3. my father / spend / most / spare time / look after / the garden

→ My father spends most of his spare time looking after the garden.

4. watching TV / most / popular / leisure activity / Britain ?

→ Is watching TV the most popular leisure activity in Britain?

5. many teenagers / addicted / the Internet / computer games 

→ Many teenagers are addicted to the Internet and computer games.

6. she / get / hooked / the medical drama / after / watch / the first people 

→ She got hooked on the medical drama after watching the first episode.

7. most / my friends / prefer / play sports / to / surf the net

→ Most of my friends prefer to play sports rather than surf the net.

8. today's world  / teenagers / rely / technology / more / the past 

→ In today's world, teenagers rely on technology more than in the past

II. Write the second sentences so that it has a similar meaning to the first one

1. It takes us more than two hours to see the film " Avatar "

→ The film " Avatar " requires more than two hours of our time to watch.

2. She likes to hang out with friends on Saturday evening

→ She's interested in socializing with friends on Saturday evening

Câu IV:

1) Xét tứ giác BFEC có

\(\widehat{BFC}=\widehat{BEC}\left(=90^0\right)\)

\(\widehat{BFC}\) và \(\widehat{BEC}\) là hai góc cùng nhìn cạnh BC

Do đó: BFEC là tứ giác nội tiếp(Dấu hiệu nhận biết tứ giác nội tiếp)

hay B,F,E,C cùng nằm trên 1 đường tròn(đpcm)

1. making

2. to lend

3. try

4. writing

5. to talk

6. to play

7. cry 

8. washing

9. to look

10. to stealing (admit to V-ing: thừa nhận đã làm gì) 

11. to go

12. to talk

13. answering

14. playing

15. to to tell