I had lots of neighbor, but the most intererting one was Nam. He lived next to my house. We came to the same school. Nam was 1 year older than me and he was a friendly man. He liked singing and playing guitar, as I could see him performing in our school. He had a sweet voice. He helped me when I'm in need, like helped me with my homework. He was such a nice and awesome neighbor!

1 : He has less=> fewer friends in his class now than he had last year.

2 : I remember that I have something new to told=> tell you.

3 : It's=> It isn't important for every students to have a book.

Tìm và sửa lỗi: it's=> it isn't important for every students to have a book

B (3) = {...;-12; -9; -6; -3; 0; 3; 6; 9; 12;...}

B (-3) = {...;-12; -9; -6; -3; 0; 3; 6; 9; 12;...}

Ư (-3) = {-3; -1; 1; 3}

Ư (6) = {-6; -3; -2; -1; 1; 2; 3; 6}

Ư (11) = {-11; -1; 1; 11}

Ư (-1) = {-1; 1}.