Exercise: Rewrite the sentence using "used to"

1. Toan loved playing badminton when he was small. 

2. She went to school on foot when she was 15 years old.

3. My hair was long and black 5 years ago. Now it’s short and yellow.

4. His father was a teacher in our school. Now he is retired.

5. Folk songs were so popular in the past. Now they aren’t anymore.

6. There was less traffic congestion 10 years ago. Now it becomes more common.

7. My grandmother was the prettiest girl in the village. 

8. My room was blue last year. Now I’ve painted it pink. 

9. This singer had little money when she was small.

10. People wrote letters to each other. Now they have mobile phones.

Vì x là số hữu tỉ nên đặt x=a/b (a,b nguyên ; (a,b)=1 (phân sô tối giản)      

Ta có : a/b + b/a =(a^2+b^2)/ab

Để a/b+b/a nguyên thì (a^2+b^2) chia hết cho ab

Vì b^2 chia hết cho b r => a^2 phải chia hết cho b mà (a,b)=1 =>a chia hết cho b

TTự : b chia hết cho a Do đó a=b hoặc a=-b Hay: x=1 hoặc x=-1
 

Rút gọn:

a, A = 2x - 3,5 - | 4x + 4,8 | - 3x + 1

b, B = - | - 4 - 2,5x | + 4x - 6,2 - 5,2x

c, C = 2,2x - 6 + | 4,2 - 1,4 x | - 3x +1,2

Help me everyone!

a) (-2,5 0,38 . 0,4) - [0,125 . 3,15 . (-8)]

b) [(-20,83) . 0,2 + (-9,17) .0,2] : [2,47 .0,5 - (-3,53) . 0,51