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

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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-2

2

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:

-2

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.