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Gọi vận tốc dự định đi quãng đường AB = x km/giờ (x>0)
thời gian dự định đi quãng đường AB = 60/x
--> vận tốc đi nửa đường đầu (đi 30km đầu) = x + 10
thời gian đi nửa đường đầu = 30/(x + 10)
--> vận tốc đi nửa đường sau (đi 30 km sau) = x - 6
thời gian đi nửa đường sau = 30/(x -6)
Theo đề ta có
30/(x + 10) + 30/(x - 6) = 60/x
1/(x + 10) + 1/(x - 6) = 2/x
x(x-6) + x(x+10) = 2(x-6)
(x+10)x^2 - 6x + x^2 +10x = 2(x^2 + 4x - 60)
2x^2 + 4x = 2x^2 + 8x - 120
4x = 120
x = 30 (thỏa mãn)
Vậy thời gian dự định đi quãng đường AB là t = 60/x = 60/30 = 2 giờ
gọi x(km) là quãng đường xe đi từ A đến B ( x∈N)
Thời gian xe đi từ a đến B là theo dự định: \(\frac{x}{50}\)
Thờ gian xe đi từ A đến B do thờ tiết xấu là : \(\frac{x}{40}\)
mà do thời tiết xấu nên xe đến chậm 1/2h
⇒ \(\frac{x}{40}-\frac{x}{50}=\frac{1}{2}\)
⇔50x-40x=100
⇔ 10x = 100
⇔ x = 10
Vậy quãng đường AB là 10km
1.Nga sometimes goes to her friend,s at the weekend.
2.We are going to Nha Trang this Sunday
3.Where are your children at the moment?
5.We eating some fruits.
1.Nga sometimes goes to her friend,s at the weekend.
2.We are going to Nha Trang this Sunday
3.Where are your children at the moment?
5.We eating some fruits.
Located in the northwest of the country, Sa Pa is a mountainous district of Lao Cai province, a land of modest, quietly but hides many wonders of the natural scene. Natural scenery of Sa Pa is combined with human creativity, along with the topography of hills, green forests, the paintings are arranged in a layout harmony to create a region with many scenes excellent romantic appeal.
Clouds floating sink in Sapa town as a city in mist fanciful, paint a picture painted marine beings. Here, there are things that are invaluable resources cool fresh air, nuanced diversity. Located at an average altitude of 1500m - 1800m, the climate is more or less back Sapa nuances of tropical origin, with an average temperature of 15-18 ° C. From May to August there is a lot of rain.
Sapa name from the Mandarin. Mandarin called Sa - Pa, "Sa" is the sand, "Pa" is the beach. Landmarks of "sand" is on the right side for 32 km from Lao Cai to Sapa. In the old days no Sapa town, residents in this area are in the marketplace, "sand" it. Therefore, local people who also say "Sa Pa market".
From the word "Sa Pa," Westerners can not pronounce, so to Sapa and they were written in French the word is "Cha Pa" and a very long time people were called "Cha Pa" within the meaning of the Vietnamese.
Sapa town still today, before there is a muddy red water circuit, so the locals called "Hung Ho", "Hung" is red, "Ho" is the age, the springs and streams of red.
Sapa has a high peak Fan Si Pan 3.143m on Hoang Lien Son range. Call Hoang Lien Son, because only on this mountain range Hoang Lien trees, a precious medicinal herbs, rare. Also the Hoang Lien is "mine" of information valuable timber species such as oil, including the birds, such as grouse, bears, monkeys, antelope and thousands of drugs. National forests Hoang Lien Son has 136 species of birds, 56 species of mammals, 553 species of insects. There are 37 mammal species recorded in the "Red Book of Vietnam. Hoang Lien Son has 864 forest plant species, including 173 species of medicinal plants.
Ham Rong mountain
Ham Rong Mountain Sapa is in adjacent towns, any visitor can also be up to the panoramic view of the town, the valley of Muong Hoa, Sa Pa, Ta Phin hidden in smog. Currently, embellished with hand of man, Ham Rong is indeed a fruitful landscape of Sapa. And, if anyone was to Shilin (Yunnan, China), the Ham Rong can also help you Shilin be imagined. Up Ham Rong, travelers lost in the gardens, clouds preferred closed body, brilliant flowers ground.
There Sapa tourism old church right in the town and from the town go back to the north east on the road to the monastery of Ta Phin has been built near the stone hillside in a clear, cool. Monasteries walk through three kilometers from north to Ta Phin Cave come with sufficient width can contain a number of regimental size of the army. In the cave stalactites create interesting shapes like the first dance, the delegation sat, meadows, woods sparkle.
Especially in Muong Hoa valley with 196 islands strange shapes carved by the ancient inhabitants thousands of thousands of years ago that many archaeologists have yet to decipher. Antique carved Zone Rated national monument.
From Sapa town, go west about 12km along the way Lai Chau, we will meet with the Silver Waterfall rushing waters pour from a height of over 200 meters, forming sounds impressive mountains.
Sa Pa is the "kingdom" of fruit, such as peach blossom, peach to yellow, small yellow peach, plum post, plum purple, plum flowers, lay single, flowering plum, flowering pear, peach blossoms, chrysanthemums, flowers ... especially pink flowers immortal live forever with time.
Sa Pa with 6 people and residents, each ethnic group has a distinct cultural capital with festivals such as Festival "POC forests" of Ta Van Giay, the festival "Span San" (mountain bike) of Mongolia, ceremony of "year dance" of the Red Dao, all festival takes place in May every year.
thường thì sau động từ to be và trước động từ chính. VD: The book was carefully written by the author
có một số trường hợp đặc biệt, trạng từ chỉ cách thức và cụm for có thể được đặt ở đầu câu hoặc cuối câu tùy vào ý nghĩa của câu. VD: Carefully written, the book is a masterpiece ( carefully đặt đầu câu để nhấn mạnh)
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