Предмет: Математика, автор: Актлек11111

Решите Пожалуйста эти уравнения

Приложения:

Ответы

Автор ответа: margaritanikolaevna
0
Добавляю  решения на 2-х фото

margaritanikolaevna: Почему-то фото не добавились, попросите больше объяснений
margaritanikolaevna: Ответы 1) Просто отнимаем от первого уравнения второе и получаем 10у=80, отсюда у=8, а х находим из любого уравнения системы, подставляя вместо у=8, получим х=-6 Ответ (-6;8) 2) Умножаем первое уравнение на 3, чтобы выровнять коэффициенты при х в каждом уравнении, получаем 3х-24у-51=0, затем вычитаем из 3х-24у-51=0 второе 3х+4у-23=0 и получаем -28у-28=0, отсюда у=-1, х находим из любого уравнения (удобнее из первого), подставляю вместо у=-1, получим х=9 Ответ (9;-1)
margaritanikolaevna: 3) Умножаем второе урав. 5х-у+17=0 на 3, чтобы выровнять коэффициенты при х в урав., получаем 15х-3у+51=0 затем от первого отнимаем второе и получаем 14у-98=0, у=7, ходим х из любого уравнения, подставляя вместо у =7 и получим х=-2 Ответ (-2;7)
margaritanikolaevna: 4) Умножаем первое уравнение на 3, а второе на 8, чтобы выровнять коэффициенты при х, получаем вместо первого 24х-27у-63=0, вместо второго 24х-16у-96=0, затем от первого отнимаем второе и получаем -11у+33=0, у=3, подставляем этот у=3 в любое уравнение и находим х=6 Ответ (6;3)
Похожие вопросы
Предмет: Английский язык, автор: ErastovaK07
ПОЖАЛУЙСТА СРОООООЧНО!!!
Water Pollution

Oceans cover more than 70 % of the Earth’s surface. Despite the vastness of this area we know little about it. Life began in the ocean more than 3.5 billion years ago. Today the ocean supports a wealth of simple and complex sea life from phyto-plankton to marine mammals. But people seem to misunderstand the importance of the ocean.
The oceans do not belong to a single nation, but are free, open territory to be enjoyed and shared. However, too often nations are very aggressive in taking the resources of the world ocean. There is widespread pollution of coastal waters, whales and dolphins are hunted to nearly extinction, and many fishing areas are depleted. Thor Heyerdahl, a famous scientist and explorer, crossed the Atlantic Ocean. They made a voyage of 4,000 kilometres. They saw 4,000 kilometres of polluted ocean. Over 5 million tons of oil products pollute the ocean each year. About 2 million tons of these products come from cars. First the oil products go into the atmosphere and pollute it. From the atmosphere the oil products go into the oceans. Big rivers carry into the ocean a lot of the waste from industry and agriculture. Pollution means death to the ocean. It kills fish and plants.
Another most important environmental problem is the shortage of clean water. Clean drinking water is a basic human need. But industrial pollution has made many sources of water undrinkable. Rivers, lakes and seas have become poisonous. Many ships sail in the ocean: water-fishing ships, ships carrying people, some carrying oil. If a ship loses some of the oil in the water or trash from the ships is put into the ocean, the water becomes dirty. Another problem is sewage systems. The sewage from many houses of a big city pollutes rivers and lakes and may even make them die.
Many fish are dying in the sea, others are getting contaminated. Fishermen catch contaminated fish which may be sold and people may get sick from eating them.
The worst problem is in the area around the Aral Sea. Cotton grown in the region needed much water, and the sea level has fallen by 14 yards. This destroyed fishing industry and led to damage in soils, crops and wildlife.
Lake Baikal is one of the world’s largest and most beautiful lakes. Russians call it Holy Sea. It contains a rich variety of animals and plants, including 1,300 rare species that do not exist anywhere else in the world. However, they are being destroyed by industrial wastes which some factories still pour into the lake every day.
A few years ago people thought that the supply of fresh water was limitless. Now clean water is scarce, and we begin to respect this resource. We must protect the clean water that remains for our children and grandchildren.


3. Написать краткий пересказ текста, выбрав важную информацию (на английском).
Предмет: Математика, автор: дипер78910