Một cửa hàng bán được 360kg gạo, sau đó nhập về 270kg thì tổng số gạo cửa hàng có là 500kg. Hỏi lúc đầu cửa hàng có bao nhiêu ki-lô-gam gạo?

Tìm hệ số của số hạng chứa x⁸ trong khai triển Nhị thức Niu tơn của n 2 x + x 2 2 n x ≠ 0 , biết số nguyên dương n thỏa mãn  C n 3 + A n 2 = 50

A.  297 512

B.  29 51

C.  97 12

D.  279 215

Read the following passage and choose the best answer for each blank.

Although some groups of people have always lived outdoors in tents, camping as we know it today only began to be (26)_______ about 50 years ago. The increase in the use of cars and improvements in camping (27) _______ have allowed more people to travel longer (28) _______ into the countryside and to stay there in greater comfort. Many campers like to be (29) _______ themselves in quiet areas, so they (30) _______ their tent and food and walk or cycle into the forests or the mountains. Others, preferring to be near people , drive to a public or privately-owned campsite (31) _______ has up-to-date facilities ,(32) _______ hot showers and swimming pools. Whether campers are (33) _______ in the mountains or on a busy site, they should remember to (34) _______ the area clean and tidy. In the forests, they must put out any fires and keep food hidden to avoid attracting (35) _______ animals.

Question: should remember to (34) _______ the area clean and tidy.

A. remain

B. stay

C. keep

D. let