b. Fill in the blanks with the Past Simple form of the verbs in brackets. (Điền vào chỗ trống với dạng đúng của thì quá khứ đơn.) 1. Last Sunday, Andy and his friends volunteered (volunteer) at the soup kitchen.  (Chủ nhật trước, Andy và bạn anh ấy làm tình nguyện ở quán ăn cho người nghèo.) 2. We______(clean up) the park near our school last weekend.  3. My parents______(raise) money to help the local children's hospital two months ago.  4. Last Monday, lots of students_______(donate) books and clothes they_____(not use) any more to poor children in their town.  5. Our school______(collect) all of the donations and sent them to poor people.  6. They ______(plant) frees in the streets to make their town cleaner. 

Phương pháp làm:
- Điền vào chỗ trống những động từ trong ngoặc với dạng quá khứ đơn.

Câu trả lời:
1. Last Sunday, Andy and his friends volunteered (volunteer) at the soup kitchen.
2. We cleaned up (clean up) the park near our school last weekend.
3. My parents raised (raise) money to help the local children's hospital two months ago.
4. Last Monday, lots of students donated (donate) books and clothes they didn't use (not use) any more to poor children in their town.
5. Our school collected (collect) all of the donations and sent them to poor people.
6. They planted (plant) trees in the streets to make their town cleaner.
- Last Sunday, Andy and his friends volunteeres at the soup kitchen.
- We cleaned up the park near our school last weekend.
- My parents raised money to help the local children's hospital two months ago.
- Last Monday, lots of students donated books and clothes they didn't use to poor children in their town.
- Our school collected all of the donations and sent them to poor people.
- They planted trees in the streets to make their town cleaner.

4. Last Monday, lots of students donated books and clothes they didn't use any more to poor children in their town.

3. My parents raised money to help the local children's hospital two months ago.

2. We cleaned up the park near our school last weekend.

Để tính giá trị của biểu thức A = x^4 - 17x^3 + 17x^2 - 17x + 20 tại x = 16, ta thực hiện các bước sau:

Thay x = 16 vào biểu thức ta được:
A = 16^4 - 17*16^3 + 17*16^2 - 17*16 + 20
= 65536 - 17*4096 + 17*256 - 17*16 + 20
= 65***2 + 4352 - 272 + 20
= 4
Vậy giá trị của biểu thức A tại x = 16 là 4.