1, mai house has a new tv 
-> there is  a new TV in Mai's house
2, minh's house í behind the drug store 
-> the  druy store is in front of Minh's house
3, l like math best 
-> my favouritr subject is Math
4, she has long black hair 
-> he hair  is long and black
5, mai , hal  better go to school on time 
-> mai should  go to school on time
6, the dog is in front on the sofa 

_> the dog sofa is    behind the dog
7, he is the dog boy with blue eyes 

-> he has   blue eyes
8, my room is smaller the har room 
-> her room   is bigger than my room
9, our garden has many flowers 
-> there are    many flowers in our garden

10, the school is to the leftof the house 
-> the house     is to the right of the school

Chứng minh: 
a(b - c) + b(c - a) + c(a - b) = 0

Chứng minh: 
a(a - 1) + 2(3 - a) + 3a = a² + 6

Tim x,y ∈ N
a, (x+1)(y+2)=4