Cho A=\(\dfrac{\sqrt{x}-3}{\sqrt{x}+1}\)

a,Tìm x để A xác định

b,Tìm x để A=\(\dfrac{1}{5}\)

c,Tìm giá trị nhỏ nhất của A

d,Tìm x thuộc Z để A thuộc Z

Read the text and then choose the best answer A, B, C or D.

Yesterday, on the way home from school, I saw an accident. A boy was run over by a taxi when he was riding his bicycle. The boy's leg was broken and it was bleeding badly. Someone there tried to stop the bleeding. They put pressure on it and held it tight. A man used his mobile phone to call the emergency service. Some minutes later, an ambulance arrived and sent the boy to the hospital. Two policemen came to the scene immediately. Some people told the police that the taxi driver was driving at a very high speed when the accident happened. Some others began talking about the traffic accidents these days and blamed the increasing number of accidents on the roads for careless driving and drunk drivers.

Question. The accident happened between a taxi and _________.

A. a bus

B. a car

C. a bicycle

D. motorbike

Cho hai số thực dương x, y bất kỳ. Khẳng định nào sau đây đúng?

A.  log 2 x 2 y = 2 log 2 x log 2 y

B.  log 2 x 2 y = 2 log 2 x + log 2 y

C.  log 2 x 2 + y = 2 log 2 x . log 2 y

D.  log 2 x 2 y = log 2 x + 2 log 2 y