Предмет: Алгебра, автор: abia24012010

3. Решите уравнение 2х⁴ + 3х² -5 = 0
Помогите пожалуйста​

Ответы

Автор ответа: Ivan19074
1

Ответ:

x=1 и x=-1

Объяснение:

Выделим квадрат двухчлена и решим:

2x^4+3x^2-5=0\\4x^4+6x^2-10=0\\4x^4+6x^2+2.25-2.25-10=0\\(2x^2+1.5)^2=12.25\\2x^2+1.5=\pm\sqrt{12.25}\\2x^2+1.5=\pm3.5\\2x^2=\pm3.5-1.5\\2x^2=2\cup2x^2=-5\\x^2=1\cup x^2=-2.5\\x=\pm\sqrt{1}\cup x\in\O\\x=\pm1\\x_1=1, x_2=-1

Следовательно, у этого уравнения есть два корня x=1 и x=-1.

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Reading Comprehension Test for 8th form Students
Directions:choose the correct letter A, B, C or D
Questions 1 through 6 refer to Text 1.
Text 1
Swift and his servant
Jonathan Swift, a famous English writer, was one day travelling on horseback with a servant. The weather was bad; it was raining and the roads were muddy. In the evening the two men came to an inn. Before going to bed, Swift told his servant to clean his boots as they were dirty. But the servant was very lazy and did not do what his master had said.
The next morning when Swift saw the dirty boots, he asked the servant why he had not executed the order. ”The roads are muddy. What is the use of cleaning the boots now? They will soon be dirty again,” the servant answered.
Swift didn’t say anything and soon told the servant to get ready because they would start at once. But the servant looked very displeased and said that he had not eaten his breakfast yet.
Swift answered that they would go without any breakfast.
”What is the use of eating now? You will be hungry again”, he said.
Questions
1. The writer and his servant were most likely travelling somewhere ....
A. in the wood
B. in the countryside
C. in the city
D. in the space
2. The servant seemed to dislike ...
A. his master
B. work
C. cleaning shoes
D. bad weather
3. Swift seemed to ...
A. be very angry
B. be quite indifferent
C. be pleased
D. be relaxed
4. The travel was to resume ...
A. shortly
B. after breakfast
C. after the rain stopped
D. after the shoes had been polished
5. The servant was possibly very ...
A. happy
B. quiet
C. hungry
D. cheerful
6. Swift was not going to _____.
A. have his shoes cleaned
B. keep the servant any longer
C. have any meal
D. leavetheinnthat day

Questions 7 through 14 refer to Text 2.
Text 2
CANADA GEESE
Canada geese can be seen and heard in many areas of British Columbia. They usually stay till November or December before flying south for the winter in search of warmer climates.
Canada geese have black heads, tails, necks and feet and white feathers on their heads. Their lifespan is quite long, ranging from twenty to thirty years. While Canada geese tend to produce young at the early age of three, females are known to reproduce up to the age of twenty, laying four to seven eggs each spring.
Canada geese have very strong family relations. In fact, both parents tend to their young for nearly a year. Families stay together until the time comes to return to the breeding areas. It is only at this time that the geese must go their separate ways. Because Canada geese are a national symbol, it is illegal to harm them in any way. This policy has actually resulted in an overpopulation of the birds. For example, in Vancouver, British Columbia, it is not uncommon to see a family of Canada geese walking around on a highway!

Questions (write + if the statement is true, or write - if it is false)
71
Canada geese are protected from hunting by the Canadian government.
+
-
8
The geese stay all winter in northern Canada.
+
-
9
Unfortunately, Canada geese have short life spans.
+
-
10
Canada geese have very colourful feathers.
+
-
11
Female geese produce many young over their lifetimes.
+
-
12
Canada geese have strong social instincts.
+
-
13
Because they avoid places populated by humans, Canada geese can only be seen in the wild.
+
-
14
Canada geese are considered a national symbol.
+
-

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