+ ΔAHB và ΔCKD có

      HB = KD (=1)

      góc AHB = góc CKD(=90º)

      AH = CK (=3).

⇒ ΔAHB = ΔCKD(c.g.c)

⇒AB = CD (hai cạnh tương ứng)

+ ΔCEB và ΔAFD có

      BE = DF (=2)

      góc BEC = góc DFA (=90º)

      CE = AF (=4).

⇒ ΔCEB = ΔAFD ( c.g.c)

⇒ BC = AD (hai cạnh tương ứng)

b) ΔABD và ΔCDB có

      AB = CD

      AD = BC

      BD cạnh chung

⇒ ΔABD = ΔCDB (c.c.c)

⇒ góc ABD = góc CDB (hai góc tương ứng)

Vậy AB // CD ( hai gó so le trong bằng nhau )

k minh nha

A B C D E F M N

(hình hơi xấu, thông cảm nha)

a) Xét \(\Delta AEB\)và \(\Delta DFC\) có: 

AE = DF

\(\widehat{AEB}=\widehat{DFC}=90^o\)

BE = CF

Do đó: \(\Delta AEB=\Delta DFC\) (c.g.c)

Suy ra: AB = DC (đpcm)

Xét \(\Delta BMC\) và \(\Delta DNA\) có:

MC = NA

\(\widehat{BMC}=\widehat{DNA}=90^o\)

BM = DN

Do đó: \(\Delta BMC=\Delta DNA\)

Suy ra: BC = AD (đpcm)

b) Xét \(\Delta ABD\) và \(\Delta CDB\) có:

AB = CD (câu a)

BC = AD (câu a)

BD là cạnh chung

Do đó: \(\Delta ABD=\Delta CDB\) (c.c.c)

Suy ra: \(\widehat{ABD}=\widehat{CDB}\) (so le trong)

=> AB // CD (đpcm)

tôi hok lớp 9 rồi nên ko biết nhưng ngày xưa hồi hok lớp hình như là ko làm bài My neighbourhood đâu

+ Hàng phím số
+ Hàng phím trên
+ Hàng phím cơ sở
+ Hàng phím dưới 
+ Hàng phím chứa phím cánh

1 . Hàng phim số 

2 . Hàng phím trên 

3 . hàng phím cơ sở

4 . Hàng phím dưới

5 . Hàng phím có chứa dấu cách

1. did- learn

2. am having

3. Is

4. have ever eaten

5. is

6. did-save

7. bought

8. didn't drink

9. does- need

10. have never enjoyed

Chúc bạn học tốt :v

Neil Amstrong is the answer !@

The first person went to the moon is Neil Amstrong.

K nha bn!

Tìm những từ Tiếng Anh bắt đầu bằng chữ y?

yes

year

yellow

you

yet 

your

yard

young

yesterday

yummy

...

year

yellow

yard

1. It is essential that you do your homework before going to school.

You must do your homework before going to school. 

2. It is necessary for us to be present at the class discussion on Saturday.

We must be present at the class discussion on Saturday.

3. Hanoi is large, Bangkok is larger and Tokyo is the largest.

Tokyo is the largest of the three cities.

4. It is wrong of us to throw rubbish..

We mustn't throw rubbish.

5. How many apples does she want?

How many apples would she ?

6. Learning how to use a computer is very easy

It is easy to learn how to use a computer.

7. He drives very carefully.

He is a careful driver.

8. Students at our school take part in a lot of outdoor activities

Students at our school do a lot of outdoor activities.

9. I find it difficult to find a better solution to that problem.

I have difficulty (in) finding a better solution to that problem.

10. Lan is the oldest of the three sisters

Lan has two younger sisters.

Chúc bạn học tốt :v 

/i:/: cheap, sleepy, peaceful, police

/i/: exciting, historic, expensive, convenient, noisy, friendly 

/i:/ : convenient 

1.such ---->so

2.lately--->late

3.that---->where

4.when--->since

5.used to--->used to

50% sai vì mk ms học lớp 7

HOCTOT

Bạn Thiên Hoàng sai 1 chút ở câu 5 nhé.

what do=>did you use to do when you felt afraid?

Học tốt.

1.It is the darkest time in my life.

2.He runs the fastest in my class.

3.She is the most beautiful girl I’ve ever met. 

4.He drives the most carelessly among us.

5.My mom is the greatest person in the world.

6.Giang is the most intelligent student in my class.

7.Nami is the tallest student in her class.

8.This is the most difficult problem in the book.

9.He drives the most carelessly. 

10.John is the youngest son.

Good luck!