Ответ по предмету Алгебра: Доведіть тотожність: (a + b)2 + (a – b)2 = 2(a2 + b2);

Предмет: Английский язык, автор: vazz9zafilghj

The lifestyle which we enjoy today is a result of countless ideas and inventions, which have taken many centuries of man’s history to develop.

1. The first great idea which started man on the road to his great achievements was when a caveman picked up a heavy stone to help him. The use of fire was another step without which no subsequent development would have been possible. But once man had learned to make and use fire, it was only a short step to discovering the use of metals. Another great move towards modern technology was the invention of the wheel by some unknown prehistoric genius.

2. Man had efficient metal weapons and was able to hunt large animals for food. Gradually, he learned to capture and tame some of the creatures, so that he could keep his food nearby until it was needed. Man also discovered how to plant crops, gathering seed from wild plants, which he knew to be useful. Once farming was established, it did not take man long to make special tools for breaking up the ground, and later he began to use the help of domestic animals in pulling his primitive plough.

3. Another important invention which has contributed greatly to our modern knowledge was writing. At first, writing was a special form of drawing, and was usually very simple. But gradually these primitive drawings turned into letters. From the counting of days and months, man went on to count cattle and sheep and the earliest forms of arithmetic appeared. The Greeks were the first people to use writing to record language as spoken by contemporary men; and their works are still widely read today, for information and for pleasure.

4. After the time of the Romans, the speed of discovery slowed down, and indeed many earlier discoveries were lost for hundreds of years. It was not until the fifteenth century, with the coming of the Renaissance, that discoveries were again made on a large scale. Europe was suddenly filled with a wish to explore the world. No less important was the invention of printing, giving many men an opportunity to read and to own books which before had been available to only the wealthy few. The spread of ideas was rapid, and led in its turn to the writing of more books. The voyagers of the Renaissance discovered the existence of many new and strange lands, and in these lands were all sorts of unknown animals and plants.

5. The seventeenth century saw a development of science. The eighteenth century is associated with many inventions and culminated in the Industrial Revolution. The invention of the steam engine, the condenser and piston made possible modern manufacturing processes. The nineteenth century was the age of the machine when man realized that many previously hard tasks could be done more easily and cheaply by machinery.
Farm machinery was invented, and production of larg-er food-crops became possible. The nineteenth century also saw the invention of electricity, which revolutionized life and made many other things possible. The manufacture of cars began a new era in transport, and led to the appearance of lorries and buses, without which our cities would not have grown to their present size.

6. The previous century was the one to see immense changes and various inventions. The airplane was constructed. During the Second World War man became aware of atomic energy and nuclear weapons. The second half of the twentieth century was characterized by the inventions of television, computers, spacecraft, genetic engineering and many others.

7. All our discoveries today are based on the ideas of men who lived before us; and without their groundwork, modern inventions would have been impossible.
With so many wonderful achievements behind him, modern man can go into an era of even greater discoveries, and all nations can benefit from the knowledge left to us by earlier generations.

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Доведіть тотожність: (a + b)2 + (a – b)2 = 2(a2 + b2);

Ответы

Доведіть тотожність:
(a + b)2 + (a – b)2 = 2(a2 + b2);