A B C D E F M N H

a/

Ta có

\(HF\perp AB;DM\perp AB\) => HF//DM. Xét tg AMD có

\(\dfrac{AF}{FM}=\dfrac{AH}{HD}\) (Talet trong tg) (1)

b/

C/m tương tự khi xét tg AND có

\(\dfrac{AE}{EN}=\dfrac{AH}{HD}\) (Talet trong tg) (2)

Xét tg AMN Từ (1) và (2) \(\Rightarrow\dfrac{AF}{FM}=\dfrac{AE}{EN}\) => EF//MN (talet đảo trong tg)

Nhẩm có nghiệm = -2

\(PT\Leftrightarrow\left(x+2\right)\left(4x^2+22x+31\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x+2=0\\4x^2+22x+31=0\end{matrix}\right.\)

Giải PT bậc 1 và PT bậc 2 để tìm nghiệm

Bạn tự làm nốt nhé

9. The dentist pulled out my tooth.

→ My tooth __________was pulled out ____________________by the dentist.

10. The police are questioning him now.

→ He _______is being questioned_______________________ now by the police

11. The waitress serves breakfast at 7 o’clock.

→ Breakfast ____is served at 7 o' clock__________________________ at 7 o’clock by the waitress.

12. Who did they give the prize to?

→ Who ____was___the prize______given_______________ to ?

13. The news seemed to have shocked him.

→ He seemed ________to be have been shocked______________________by the news.

14. You should take these tablets before meals.

→ These tablets _____should be taken_________________________ before meals.

15. The teacher has sent him out of the classroom.

→ He _________has been sent_____________________out of the classroom by the teacher.

16. You must wash coloured clothes separately.

→ Coloured clothes _________must be washed_____________________separately.

17. The mayor will open the new sports center next month.

→ The new sports center ______will be opened________________________by the mayor next month.

18. Many parents influence their children strongly.

→ Children __________are influenced____________________ strongly by most parents.

19. They were pulling down the building when I walked by.

→ The building _______was being pulled_______________________down when I walked by.

20. Somebody has stolen Jack's car recently.

→ Jack’s car _________has been stolen_____________________ recently.

21. He expects people to show him more respect.

→ He expects _________to be showed_____________________more respect.

22. Nobody has seen the Queen since July.

→ The Queen _______hasn't been seen_______________________ since July.

\(A=\dfrac{2x+1}{x-8}\)

\(A=\dfrac{2x-16+17}{x-8}\)

\(A=2+\dfrac{17}{x-8}\)

A nguyên \(\Leftrightarrow\dfrac{17}{x-8}\) nguyên

\(\Leftrightarrow x-8\in\text{Ư}\left(17\right)=\left\{\pm1;\pm17\right\}\)

+) x - 8 = 1 <=> x = 9

+) x - 8 = -1 <=> x = 7

+) x - 8 = 17 <=> x = 25

+) x - 8 = -17 <=> x = -9

\(A=\dfrac{2x+2}{x-8}=\dfrac{2x-16+18}{x-8}=\dfrac{2\left(x-8\right)+18}{x-8}=2+\dfrac{18}{x-8}\)

Để A nguyên

\(\Leftrightarrow\dfrac{18}{x-8}\) nguyên

<=> x - 8 thuộc Ư(18) = \(\left\{\pm1;\pm2;\pm3;\pm6;\pm9;\pm18\right\}\)

Bảng tìm x 

Vậy .........................

\(A=\dfrac{2\left(x-8\right)+17}{x-8}=2+\dfrac{17}{x-8}\Rightarrow x-8\inƯ\left(17\right)=\left\{\pm1;\pm17\right\}\)