Предмет: Алгебра, автор: LOL100998

Если туристы будут проходить в день на 5 км больше ,чем сейчас ,то они пройдут за 6 дней расстояние ,большее 90 км .Если же они будут проходить в день на 5 км меньше ,то за 8 дней они пройдут расстояние ,меньшее 90 км.Сколько километровв день проходят туристы?

Ответы

Автор ответа: denis60

Пусть туристы проходят сейчас в день х километров, тогда по условиям задачи можно составить 2 неравенства: $left { {{(x+5)cdot6>90} atop {(x-5)cdot8<90}} right.\left { {{6x+30>90} atop {8x-40<90}} right.\left { {{6x>60} atop {8x<130}} right.\left { {{x>10} atop {x<16,25}} right.$

Следовательно, х может иметь значения от 10 до 16,25, не включая эти числа. Если нужно найти целочисленные значения, то это могут быть числа: 11; 12; 13; 14; 15; 16.(километров)

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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.

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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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