Current location - Training Enrollment Network - Mathematics courses - Eighth grade, the first volume of Beijing Normal University, the second chapter of mathematics, pages 49 to 52, review the answers.
Eighth grade, the first volume of Beijing Normal University, the second chapter of mathematics, pages 49 to 52, review the answers.
1. 1.2, 0, √ 18, 10/7, √2 1, √ 14, 10

2.( 1) 5; (2)5; (3) 5. Practice 2.4 Knowledge and Skills

1. 13, 10, 4/7, 3/2, √ 18

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2.( 1) 19; (2) — 1 1; (3) 14。

3.( 1)x = 7; (2)x= 5/9

4.( 1)4; (2)4; (3)0.8 contact extension

5. not necessarily.

2.3 cube root

1.0.5, a 4.5, 16.2.6 cm. Exercise 2.5 Knowledge and Skills

1.0. 1, 1, 1, 20, 2/3, 8.

2.2, 1/4, 1 3, 125, 1 3

Mathematical understanding

4.( 1) No, yes; (2) Both of them increase with the increase of positive K value; (3) Increase

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5.5 cm contact extension

6.2 times, 3 times, 10 times, n times.

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2.4 How wide is the park?

1.( 1) 3.6 or 3.7; (2)9 or 10

2.√6 & lt; 2.5 Practice 2.6 Knowledge and Skills

1.(i) 6 or 7; (2)5.0 or 5. 1

2.( 1)(√3— 1)/2 & lt; 1/2(2)√ 15 & gt; 3.85

3.(√5— 1)/2 & lt; 5/8 mathematical comprehension

4.( 1) is wrong because (√8955) is obviously greater than10; (2) Wrong, because (√ 12345) is obviously less than 100. Problem solved.

5.4m, where only the residual approximation of 4m can be taken, and 3m.6. ≈ 5m cannot be taken.

2.5 Use a calculator to write prescriptions.

( 1)(√ 1 1)& lt; √5.(2)5/8 >(√5— 1)/2。

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Knowledge and skills

1.( 1)49; (2) 2.704; (3) 1.828; (4)8.2 16

2.( 1)√8 & lt; √25; (2)8/ 13 >(√5— 1)/2。

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Mathematical understanding

3. With the increase of the times of square root, the result tends to 1 or1L.

4.( 1) The result is getting smaller and smaller, and tends to 0; (2) The results are getting bigger and bigger, but they tend to practice in class with real numbers of 0.2.6.

1.( 1) wrong (all infinite decimals are not irrational);

(2)x (the irrational part is an infinite acyclic decimal);

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(3) Wrong (numbers with roots are not necessarily irrational).

2.( 1) √7, 1/√ 7, √ 7; (2) 2,1/kloc-0, 2 (3)17,1/7, 7 3. Omit exercise 2.8.

( 1){ 1 7.5,4,2/3, 1 √ 27,0.3 1,0. 15? );

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(2) { √ 15,√(9/ 17),—∏? );

(3) {√ 15,4, √(9/ 17), 2/3, 0.3 1, 0. 15) (4) {-7.5, 1 √27,-∏}

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2.( 1)–3.8, 5/ 19, 3.8.(2) √ 2 1,I√2 1/2 1;

③∏,a 1/∏,∏; (4) 3, √3/3, √ 3; (5) 3/10,13, 3/10 3.

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1.( 1)3/2; (2)3; (3) 3- 1; (4) 13-4 √ 3 Exercise 2.9 Knowledge and Skills

1. Solution: (1) Original formula =1; (2) Original formula = 1/2

(3) The original formula = 7+2 √10; (4) Original formula =1;

problem solving

2.S △ ABC = 5。 (hint: AB=√ 10, BC = ∠ 10, ∠ ABC = 90). Practice in class.

1.( 1)3√2; (2) 2 √ 3; (3) √ 14/7; Exercise 2. 10

Knowledge and skills

1.( 1)3√2; (2) 14 √ 2; (3) 20√3/2; (4) 5 10/2. Knowledge and skills

1.( 1){ √ 1 1,0.3,∏/2,√25,0.575 775 777 5,? (2){ 1 1/7, √-27,? }

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(3){ 1 1/7, 0.3, √25, 1 √25, 0,? }(4){ √ 1 1,∏/2,0.575 775 777 5,? }

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2.( 1) 1.5, 1.5; (2) 19, 19; (3) 7/6,7/6; (4) 10, 10

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3.( 1) 8; (2)0.2; (3) one third; (4) 10.

4.( 1)5/ 1 1; (2)0.5; (3) a 2/9; (4) 1(5)-5/3; (6) 10:

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5.( 1)8.66; (2) 5.37; (3)2.49; (4) 10.48; (5) 89.44.

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6.( 1) 6.7 or 6.6; (2)5 or 4.

7.( 1) ∣- 1.5 ∣ < 1.5; (2) 1 √ 2

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8.( 1) 1; (2)5; (3) 1; (4) 16 √3; (5) 55 √ 7/7; (6)7√2/2

9.( 1) Point A stands for a √ 5; (2) 1√5 & gt; One, two and a half

10. Area: (1/2)? 2? 1= 1; Circumference: 2+2 √ 2 ≈ 4.83. Mathematical understanding

13.( 1)0. 1; (2)0; (3)0. 1; (4)0, 1; (5) 1,2,3; (6) 1,0, 1,2.

14.( 1) Wrong (such as irrational number); (2) Error (such as √2+ (1 √ 2) = 0). 15. Wrong. Solve the problem.

16.≈ 1.77cm。

17.≈ 1.6m

18.≈ 13.3 cm. ≈4.24 20.≈42

21.≈ 78.38km/h

22.≈23.20 cm

23. 19.26 (∩), the electrical appliance is a.