“Bỗng nhận ra hương ổi
Phả vào trong gió se
Sương chùng chình qua ngõ
Hình như thu đã về”

There are four people in my family – my parents, my little sister and I. I love them all, but my favorite one is my mother. Her name is Mai, and she is 42 years old at the moment. She works as a manager at a furniture store, therefore she is quite busy. She leaves home at 7 and a half in the morning after making breakfast for the whole family, and she usually comes home late in the evening. She is a beautiful woman with an ideal height, long curly hair and a pair of big round eyes. However, because she spends too much time and effort on her work, she starts to have some signs of old aging such as small wrinkles and freckles on her skin. Since she has to work with many employees, she usually has a serious look on her face, and her voice is a little bit loud. However, she is actually a very nice and outgoing person. She always tries to help the staffs with their work, and she is very devoted to her job. At home, she talks to us in a more gentle voice, and there are very few times when she scolds us. She rarely has time to relax and take care of herself, but some of her favorite things to do when she has any spare time are reading novels, watching romantic movies, and chatting with us. I know she works under a lot of pressures, so I always talks to her about funny and interesting things at my school, and she seems to enjoy my stories very much. My mother is such a great woman when she can be both a good supervisor and a good mother. I love her a lot, and she is my goal to strive for my future.

Tổng của 4 số trên là :

      45 x 4 = 180

Nếu không kể số thứ nhất thì tổng 3 số còn lại là :

     40 x 3 = 120

Số thứ nhất là :

     180 - 120 = 60

Số thứ nhất lớn hơn trung bình cộng của 4 số trên :

      60 - 45 = 15 ( đơn vị )

tổng 2 số:42x2=84

nếu thêm số 48 thì tổng là:84+48=132

Trung bình:132:3=44

Ta có tan 80 = cot 10o; tan 70o = cot 20o; tan 50o = cot 40o; tan 60o = cot 30o và

tan .cot  = 1

Nên B = tan 10o. tan 20o. tan 30o. tan 40o. tan 50o. tan 60o. tan 70o. tan 80o

= tan 10o. tan 20o. tan 30o. tan 40o. cot 40o. cot 30o. cot 20o. cot 10o

= (tan 10o. cot 10o) . (tan 20o. cot 20o) . (tan 30o. cot 30o) . (tan 40o. cot 40o)

= 1.1.1.1 = 1