Предмет: Алгебра, автор: janes16

решите уравнение: (4x+1)^2-(5-2x)^2

Ответы

Автор ответа: AltynkaIslu

1)выносим за скобки 16х^2+8x+8-25+20x-4x^2=12x^2+28x-17

2) решаем квадратное уравнение : 12x^2+28x-17=0

D=b^2-4ac=1600

x1=-28-40/24=-68/24

x2=1/2

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DEVELOPMENT OF TELECOMMUNICATIONS
Early telecommunications included smoke signals and drums. In 1792, a French engineer,
Claude Chappe built the first visual telegraphy (or semaphore) system between Lille and Paris.
However semaphore as a communication system suffered from the need for skilled operators and
expensive towers often at intervals of only ten to thirty kilometres.
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April 1839.
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version of the electrical telegraph. The patented invention proved successful and by 1851
telegraph lines in the United States spanned over 20,000 miles (32,000 kilometres).
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allowing transatlantic telecommunication for the first time. The international use of the telegraph
has sometimes been dubbed the "Victorian Internet".
The electric telephone was invented in the 1870s, based on earlier work with harmonic
(multi-signal) telegraphs. The first commercial telephone services were set up in 1878 and 1879
on both sides of the Atlantic in the cities of New Haven and London. Alexander Graham Bell
held the master patent for the telephone that was needed for such services in both countries.
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countries.
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passing through a centralized mainframe. A four-node network emerged on December 5, 1969.
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1. Read and translate the text. Answer the following questions.

1. What did early telecommunications include?

2. Who built the first semaphore system?

3. What did semaphore as a communication system suffer from?

4. When was the first commercial electric telegraph constructed?

5. It used the deflection of needles to represent messages, didn't it?

6. What did Samuel Morse do on the other side of the Atlantic Ocean?

7. What happened on 27 July 1866?

8. Has the international use of the telegraph sometimes been dubbed the "Victorian Internet”?

9. What do you know about the first commercial telephone services?

10. What did Guglielmo Marconi do in December 1901?

2. Translate the following equivalents from the text and memorize them.

Smoke signals, visual telegraphy, skilled operators, to represent messages, the patented invention, transatlantic communication, to establish wireless communication, to investigate packet switching, to become widespread, orbiting satellites.

3. Multiple choice:

1. The first ..... was constructed in England by Sir Charles Wheatstone and Sir William Fothergill Cooke:

a) moving picture;

b) electrical telegraph;

c) lightning rod.

2. ......., Guglielmo Marconi established wireless communication between Britain and Newfoundland.

a) In December, 1901;

b) On March, 1925;

c) On April, 1839.

3. The spread of ..... allowed television networks to spread across large countries.

a) electrical telegraph;

b) commercial telephone services;

c) coaxial cable and microwave radio relay.

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