đề sai bạn nhé

dung la sai that tui sua 2;45 thanh 2,45

Hủy diệt, hủy bỏ, phá hủy

huỷ hoại

Phá huỷ 

mik tìm được từng này thôi

3a + 4 không chứa b em xem lại xem đã ghi đúng đề bài chưa nhé. 

An kiểu -_-

thầy giao sai đề

Lời giải:
Đặt $\underbrace{1111....111}_{50}=a$

$\Rightarrow 9a+1=10^{50}$

$A-B=\underbrace{111....1}_{100}- \underbrace{2222....2}_{50}$

$=\underbrace{111...1}_{50}.10^{50}+\underbrace{111....1}_{50}+\underbrace{2222....2}_{50}$

$=a(9a+1)+a-2a = 9a^2=(3a)^2$ là scp 
Ta có đpcm.

$x,y$ có điều kiện gì không bạn? Là số nguyên, số tự nhiên hay một số bất kỳ?

Task 1: Give the correct word form of these words in brackets.

1. A map is really ...helpful........... when travelling.( help)

2. Is .......tourism........ the world's larghest industry ( tour)

3. Vietnam is becoming one of the world's top destinations with its endless natural .........beauty..... ( beautiful )

4. The total ...........population.......... of France has been increasing for years now, reaching 67 million inhabitants in 2021 ( populate)

5. The Han River is popular with both...........locals... and visitors( location)

6. When is Bui Vien Steet always ......crowded......?( crowd)

7. Filipion and English are official ..........languages...... of the Philippines ( language)

8. India is the second most .........populous.... country in the world. ( pollution )

9. The Dubai Miracle Garden is a .......colorful...... flower garden located in the district of Dubailand, Dubai, United Arab Emirates( colour)

10. Being a .....coastal ...... city, Quy Nhon is a great place for seafood lovers. ( coast)

1. My children are ........taking........ their first trip to Korea.

2. Could you .........lend...... me your car? Mine broke down yesterday

3. We ........borrowed......... Lucy's umbrella because it raianed heavily yesterday morning

4. What time does the plane .....take off........ ?

5. Japan is ......famous........ for cherry blossoms and Mount Fuji.

6. There is a festival near here, so it's ...........welcoming.......... people coming to join\

7. How did you ...feel......... after the trip?

8. Her parents ......look forward to... visiting Ha Long Bay this weekend.

9. The Golden Bridge in Da Nang .........is held in the....... hands of the Mountain God.

10. Vietnamese people are ....proud of..... their cuisine culture

\(B=\left(1+\dfrac{1}{1\cdot3}\right)\left(1+\dfrac{1}{2\cdot4}\right)\cdot...\cdot\left(1+\dfrac{1}{2020\cdot2022}\right)\)

\(=\left(1+\dfrac{1}{2^2-1}\right)\cdot\left(1+\dfrac{1}{3^2-1}\right)\cdot...\cdot\left(1+\dfrac{1}{2021^2-1}\right)\)

\(=\dfrac{2^2-1+2}{2^2-1}\cdot\dfrac{3^2-1+1}{3^2-1}\cdot...\cdot\dfrac{2021^2-1+1}{2021^2-1}\)

\(=\dfrac{2^2}{\left(2-1\right)\left(2+1\right)}\cdot\dfrac{3^2}{\left(3-1\right)\left(3+1\right)}\cdot...\cdot\dfrac{2021^2}{\left(2021-1\right)\left(2021+1\right)}\)

\(=\dfrac{2\cdot3\cdot...\cdot2021}{1\cdot2\cdot3\cdot...\cdot2020}\cdot\dfrac{2\cdot3\cdot...\cdot2021}{3\cdot4\cdot...\cdot2022}\)

\(=\dfrac{2021}{1}\cdot\dfrac{2}{2022}=\dfrac{2021}{1011}\)

a )7,8-7,8+96,4+3,6

 = 0 + 96,4 + 3,6 

 = 0 + 100

 = 100