Tài liệu ôn tập Đại số Khối 8

Nguyễn ThịMinh Phương

Mục lục

Chương 1. Rút gọn biểu thức 2

Chương 2. Câu hỏi sau bài rút gọn 5

2.1. Dạng 1: Tìm x đểP = ? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.2. Dạng 2: Tính giá trịcủa biểu thức . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.3. Dạng 3: Tìm x đểP > ?, P < ? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.4. Dạng 4: Chứng minh hoặc So sánh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.5. Dạng 5: Tìm x ∈Z đểP ∈Z . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

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Nguyễn ThịMinh Phương

Chương 1

Rút gọn biểu thức

1. (x −2)(x −2) −(x + 2)(x + 2).................................................................................................. −8x

2. (x −1)(x −1) −(x + 1)(x + 1)..................................................................................................... −4x

3. (x −2)(x + 1) −(x + 2)(x −1)..................................................................................................... −2x

4. (x−1)(x+1)+(x−2)(x+2).....................................................................................................2x2 −5

5. (x + 1)(x2 −x + 1) −x3 + 2...................................................................................................3

6. x2 + x −1 −(x2 + 2) −(x + 1)(x −1).......................................................................... −x2 + x −2

7. x2 + 2 + (x + 1)2 −2(x2 + x + 1)...........................................................................................1

8. 15x −11 −(3x −2)(x + 3) −(2x + 3)(x −1).............................................................. −5x2 + 7x −2

9. (x −1)(x −2) −(x + 3)(x + 1) −(x2 + 5)......................................................................... −x2 −7x −6

10. (x + 2)(x −2) −(x + 1)(x −3) −(3x2 −1).................................................................... −3x2 + 2x

11. (x −3)(x −1) −(2x −1)(x −2) + x2 −2.............................................................................x −1

12. (x + 1)2 + (x −1)2 −(3x + 1)..............................................................................(x −1)(2x −1)

13. (x + 1)x + 3(x −1) −(6x −4)......................................................................................(x −1)2

14. 2x−9−(x+3)(x−3)+(2x+1)(x−2)..........................................................................(x+1)(x−2)

15. 2x(x −3) + (x + 1)(x + 3) −(3 −11x)...............................................................................3x(x + 3)

16. 2x x + 3 + x + 1

x −3 + 3 −11x

9 −x ......................................................................................................... 3x

x −3 17. 2x −9 x2 −5x + 6 −x + 3

x −2 −2x + 1

3 −x ...............................................................................................x + 1

x −3 18. x x −1 + 3 x + 1 −6x −4

x2 −1.......................................................................................................x −1

x + 1

19. x3 + 26x −19

x2 + 2x −3 − 2x x −1 + x −3

x + 3.......................................................................................x2 + 16

x + 3

20. 2x2 + 4

x3 −1 + x + 2 x2 + x + 1 − 2 x −1................................................................................ x x2 + x + 1

21. x3 −1

x2 −x −x3 + 1

x2 + x −x2 + 1

x ................................................................................(x + 1)2

x

22. x4 −x x2 + x + 1 − x4 + x x2 −x + 1 + x2 + 1.....................................................................................(x −1)2

23.

24.

25. 1

x + x x + 1

: x x2 + x................................................................................x2 + x + 1

x

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