Ta có : P(0)=\(a\times0^2+b\times0+c\)

P(0) = c \(⋮\) 3

P(1) = \(a\times1^2+b\times1+c\)

P(1) = a+ b+ c \(⋮\) 3

mà c \(⋮\) 3

=> a + b \(⋮\)3 => 2a+2b \(⋮\)3 (1)

P(2) = a . 2² + b. 2 + c = 4a + 2b + c

mà c \(⋮\) 3

=> 4a + 2b \(⋮\)3 (2)

từ (1) và (2) , ta có : (4a+2b) - ( 2a+2b) = 4a + 2b - 2a - 2b = 2a \(⋮\) 3

Vì 2 \(⋮̸\)3 => a \(⋮\)3

=Vì a \(⋮\)3

mà a+b \(⋮\)3

=> b \(⋮\)3

Vậy a , b , c \(⋮\)3

Thất bại là nền tảng cho sự thành công =)

1. Mary / be / both / young / pretty.

=> Mary is both young and pretty.

2. I / be / afraid / I / can not come / your birthday party. I am afraid that I can not come to your birthday party .

3. What time / you / get / work / yesterday / morning / ? / .

What time did you get to work yesterday morning ?

4. How long / it / take / you / get / school / ? /

How long does it take you to get to school ?

5. I / not / interested / find / new / job.

I am not interested in finding a new job .

6. My father / like / listen / music / the evenings.

My father likes listening to music in the evening.

7. There / some / tall buildings / this town / ? /

Are there some tall buildings in this town?

8. My friends / I / often / go / fish / the summer.

My friends and I often go fishing in the summer.

9They / look / forward / meet / old / friends / again.

They are looking forwark to meeting old friends again.

10. It / important / you / do / your homework / before / you / class.

It is important that you do your homework before you go to class.

26. She likes staying at home. (stay)

27. I haven't seen him since yesterday afternoon. (not see)

28. Children ought to cross the street carefully. (cross)

29. The sun never rises in the west. (rise)

30. Look! Some boys are playing soccer in the school yard. (play)