nguyên tố R tạo với hidro hợp chất có CTHH là RH4. biết thành phần khối lượng của hidro trong hợp chất là 25%.Xác định nguyên tố R

giải giúp mik với mik đang cần gấp bài 1 tính tổng tất cả các số nguyên x biết a. -10<x<17 b.-3<x< hoặc = 3 c. |x|<6

Giúp mich hình với. Mich cần gấp

Giúp em giải câu b,2x+12-3x=-21

tại sao gọi là bình nguyên bồi tụ

479+395-567+432-243=? giup em vs

C. READING I. Fill ONE suitable word into each of numbered blaks in the passage. Australia is a big country, but nearly all Australians live near the sea. On hot summer days, you can see thousands of people at the beach. Many beaches have waves (1)______ are very high. These large waves are known as surf and the people who ride them are called surfers. Surfing is a skill, and it needs learning. Don’t (2)______ to be able to surf properly the (3)______ time you try. However, by practising a few times you will learn (4)______ to do it. Surfing is not a new sport. Perhaps its origins need explaining. It started hundreds (5)______ years ago in Hawaii. Men swam (6)______ to sea to catch fish and found they could come back to land very quickly by riding the waves. These first surfers did not (7)______ a board. They were “body surfers”. Many people (8)______ do this type of surfing today. After a while people started to use boards and rode the waves by lying, kneeling or standing (9)______ them. These first surfboards were made of wood and the water made them rot after a while. Today, surfboards are made of plastic or fibreglass (10)______.

MN giúp mk phần trắc nghiệm với nhé

1 a)100+(-520)+1140+(-520) b)13-18-(-42)-15 c)(-12)×(-13)+(-22) e)-657-(-313)+(-313+657)+201 f)(-4)³+(-6)²

cho hình thang cân ABCD (AB//CD) biết BD=7cm, góc ABD= 45 độ, tính S hình thang ABCD