Chiều cao tam giác là:

\(\dfrac{13,8*2}{2,3}=12\)(cm)

Độ dài đáy là:

30,5-12=18,5(cm)

Diện tích tam giác lúc đầu là:

18,5*12:2=111(cm²)

Đáp số:111cm²

A/ Ta có: \(\widehat{B_1}=\widehat{D_1}=60^o\)

Mà 2 góc này ở vị trí đồng vị 

Nên a//b

=> \(\widehat{ACD}=\widehat{CAB}=90^o\)( 2 góc so le trong)

=> c⊥b

b/ Ta có : \(\widehat{B_1}+\widehat{B_2}=180^o\)( 2 góc kề bù)

=> \(\widehat{B_2}=180^o-\widehat{B_1} \)

=>\(\widehat{B_2}=180^o-60^o=120^o \)

=> \(\widehat{B_4}=\widehat{B_2}=120^o\)(đối đỉnh)

Ta có: \(\widehat{B_1}=\widehat{B_3}=60^o\)(đối đỉnh)

21-> I was given a lot of presents by my parents. 

-> A lot of presents were given to me by my parents.

22. We are delighted that everyone enjoys our homemade cakes.

23. He is so pleased that his parents are waiting at the school gate to take him home.

24. I am so happy that my brother got a safe flight.

25. We are so afraid that we can't join the party with you.

Bài 1: Tìm x

a) (2x-1) ² - 25 = 0

<=> (2x-1)² =  25

<=>  2x-1 = 5  hay 2x-1 =-5

<=>  2x= 6      hay  2x=-4

<=>   x=3     hay    x= -2

Vậy S={3; -2}
b) 3x (x-1) + x - 1 = 0

<=> (x-1)(3x+1)=0

<=> x-1=0  hay  3x+1=0

<=> x=1 hay 3x=-1

<=> x=1 hay x=\(\dfrac{-1}{3}\)

Vậy S={1;\(\dfrac{-1}{3}\)}

c) 2(x+3) - x ² - 3x = 0

<=> 2(x+3)- x(x+3)=0

<=> (x+3)(2-x)=0

<=> x+3=0 hay 2-x=0

<=> x=-3  hay  x=2

Vậy S={-3;2}
d) x(x - 2) + 3x - 6 = 0

<=> x(x-2)+3(x-2)=0

<=> (x-2)(x+3)=0

<=> x-2=0 hay x+3=0

<=> x=2 hay x=-3

Vậy S={2;-3}
e) 4x ² - 4x +1 = 0

<=> (2x-1)²=0

<=> 2x-1=0

<=> 2x=1

<=> x=\(\dfrac{1}{2}\)

Vậy S={\(\dfrac{1}{2}\)}
f) x +5x²  = 0

<=> x(1+5x)=0

<=>x=0 hay 1+5x=0

<=> x=0 hay 5x=-1

<=> x=0 hay x= \(\dfrac{-1}{5}\)

Vậy S={0;\(\dfrac{-1}{5}\)}
g) x ²+ 2x -3 = 0

<=> x²-x+3x-3=0

<=> x(x-1)+3(x-1)=0

<=>  (x-1)(x+3)=0

<=> x-1=0 hay x+3=0

<=> x=1  hay x=-3

Vậy S={1;-3}

vì cold là tính từ thì mk dùng động từ to be ấy

I. Choose the correct answer. 

1. She _____ the book last night.

A. Read​ B. Reads ​C. Readed

2. An Nhien is _____  ______ (tall) student in my class.

A. A tallest​B. The tallest​C. taller than

3. _____ it _____ sunny tomorrow?

A. Will – be​B. Is – be​C. Will – is

4. Hannah is a ______ student.

A. Better​B. good​C. well

5. She sang a song _____.

A. Loud​B. Loudly​C. Nice

6. Last night, She _____ sick.

A. Was​B. is​C. were

7. Which is ___________ soccer team in your country?

A. The best​B. The good​C. The better​D. good

8. There are ______ books on the table.

A. Some​B. Any​​C. None

9. Are there ______ books on the desk?

A. Some​B. Any​​C. None

10. New Year’s Day is _____ January.

A. On​​B. In​​C. At

11. Look! The car ______.

A. Is coming​B. came​C. comes

12. She ________ to school by bus.

A. Is often go​​B. often goes​C. goes often

13. At 7pm last night, I ________ my homework.

A. Doing​B. did​C. was doing​D. have done​

14. I __________ English for over 3 years.

A. Learned​B. Have learnt​​C. learn

15. There _________ teddy bears under my chair last night.

A. Were any​B. are any​C. is some​D. were some

1.developing

2.enviromentalists

3.flying

4.discoverer

5.scientist

6.inventor

7.productive

8.researchers

a

       \(5x^2-3=0 \)

<=> 5x² =3

<=> x²= \(\dfrac{3}{5}\)

<=>\(x=\sqrt{\dfrac{3}{5}}\)hay \(x=-\sqrt{\dfrac{3}{5}}\)

Vậy S={\(\sqrt{\dfrac{3}{5}}\);\(-\sqrt{\dfrac{3}{5}} \)}

     4x³+x=0

<=> x(4x²+1)=0

<=>x=0 hay 4x²+1=0

<=> x=0 hay 4x²=-1(vô lý)

Vậy S={0}

C Complete each second sentence using the word given, so that it has a similar meaning to the first sentence. Write between two and five words.

17 Jack really likes football and never misses a match. crazy

J a c k ............is crazy about......................................................football and never misses a match.

18 My uncle worked on a sailing boat until he was thirty, was

My uncle........was a sailor..................... until he was thirty.

19 Do you want to watch TV? Feel

Do you ....feel like watching....................TV?

20 John participated in a swimming competition last week, part John............took part in.......................in a swimming competition last week. 21 June and I had a game of tennis, against

I had ..a game of tennis  against June.

22 I played chess almost every day when I was young, used

I used to play c chess almost every day when I was young.

23 Volleyball doesn’t really interest me. In

I’m not really interested in  volleyball.

24 I enjoyed myself at your birthday party, fun

I had fun at your birthday party.

25 Young children like Disneyland, popular

Disneyland is popular with young children.

26 Karen doesn’t like watching sport on TV. Keen

Karen isn't keen on watching sport on TV.