My brother is in HCM city. He (1).....is...... a teacher of math. He goes to work (2)...from....... Monday to Saturday. The school starts (3) ...at......... 7.00 in the morning and (4) .....finishes....... at eleven fifty. After work, he comes back (5) ..........home....... and has lunch at (6) ..a.......... quater past twelve. In the afternoon, he (7) .....does....... the housework and plays games. In the (8) ......afternoon......... after dinner he watches TV or (9) .........reads........... books. He go to bed at half (10) ....past.............. eleven.

there wasn't many people in the shop
→there were.....a few people in the shop......

M=2016^2015+2016^2014=2016^2014(2016+1)=2016^2014.2017 chia hết cho 2017 (đpcm)

What did you do the last time you had a bad toothache ?

1.Mr Nam teacher math in my school

A B C D teacher -> teaches

2.What does Lan and Nga do after school ?

A B C D does -> do

3.It is very noise here

A B C D noise -> noisy

4.There aren't any store here

A B C D store -> stores

5.Is the lake from the right of the house?

A B C D from -> to

Ta có n(n+1) chia hết cho 2 với mọi n E N.

Với n=3k ta có 3k(3k+1)(6k+1) chia hết cho 3 và tích chia hết cho 6

n=3k+1 ta có (3k+1)(3k+2)(6k+3)=3(3k+1)(3k+2)(2k+1) chia hết cho 6

n=3k+2 ta có (3k+2)(3k+3)(6k+5)=3(3k+2)(k+1)(6k+5) chia hết cho 6. kết hợp các điều trên ta có đpcm