A: “How far is it from your house to the bus stop?” - B: “…………….”

A. It’s about 15 minutes.

B. It’s about half an hour.

C. It’s only about 450 meters.

A: “Excuse me. I’m looking for a drugstore. Could you tell me how to get there?” - B: “…………..”

A. Thank you. I can do it myself.

B. Go straight ahead. Take the fourth street on the right. It’s on your right.

C. Don’t mention it.

A: “Could you tell me where the grocery store is?” - B: “……….”

A. Yes. I think you’re right.

B. Yes, I could.

C. Yes, there’s one right next to this factory.

Xét tính đơn điệu của các hàm số sau:

a) 

b) 

Ta sẽ khuấy đều hỗn hợp đường với cát cho đến khi đường tan thì ta thu đc cát