Bài tập chuyên đề rút gọn lớp 8 hay. giúp học sinh có thêm nhiều sự rèn luyện, cố gắng, chăm chỉ trong việc hoàn thành công việc học tập của mìng...................................................................................................................................
Trang 1Rút gọn biểu thức sau: Đáp án
x 3x x 4x 3 x 1
x 2 x 2 4 x
3. C 1 x 1 2x x(1 x)2
3 x 3 x 9 x
2x 6x x 9
x 2x 1 x 1 x 2x 1
6.
2
x 1
1 x
x 2x 2 x x 4x
9. I 4x2 33x 17 22x 1 6x 2
x 1 x x 1 x x
10. K = x2 9y2 2 3y
x 9y x 3xy
x 1 x x 1 x x
K
x 1 x (x 1) x 1
x 9 3 x x 3
14.
N
x y 1 y x y 1 x 1 x 1 y
5x 20 x 8x 16
8x 18 2x 3x 4x 6
2x 3x 2x 3 9 4x
3x 2y 3x 2y
x 2 x 2 4 x x 8
2x 2x 1 2x 4x
1. x 2
x 3
2. x 2
x 2
3.
2
10x
9 x
4.
2
51x 15 2x x 9
5.
2
10x 10
x 1 x 1
6 1
7.
2
2
1 x
8. 1
x2
9.
2
12
x x 1
10.
x 3y
x x 3y
11.
3
12x
x 1
12.
2
5x
x x 1
13. 6x
x 3
14 x-y+xy
15.
2
2
6x 29x
5 x 4
16.
2
2
x 4x 3
x 4x 9
17. 8 2x3
18 2y-3x
19. 1
x2
20. 1 x
21. 12 x
Trang 221. A= 6x 12 6x 12 x 2 36
x 6x x 6x x 1
x 10 x 2 x 10 x 2
:
24.
2
y y 3y y 3 y D
3 y 2y 3 y 3y y 9
x 36 x 6x x 6x 6 x
: x 2
27.
2
x 2 2 2 4x x 3x 1
28.
2
2
1 2x x 2x 24 12x
4 2x 3x 6 3x 12 6 13x
29.
x x x x 1 x 1 x
1 x 1 x 1 x 1 x
30.
5x 1 1 2x 2 2x
x 1 x x 1 1 x x 1
a b 4ab a b b a N
33.
x x 8 x 2x 4 4
x 2 x 8 x 4 2 x
34.
2
x 1 x x 1 1 x 2
35.
2
x x x 1 x 1 x 1 x x x 1
36.
2
x 9 x 3 x 2 x 2 x 3
37.
2
x 1 x 1 x x 1
1 x x x 2x x 1 2x x x
4x x 2 2 3x x 4
x 4 2x 4 x 4x x 2
22. x 1
x 2
23. x 1
x 1
24 -1
25 -1
26. 1
2 x
27. x 1 3
28. 2
x2
29.
2
2
x
1 x
30.
2
2
x
x x 1
31. 2x 2
x
32 2b
33. 1
x 2
34.
2
2
x x 1
35. x 1
x 1
36. 3
x2
37.
2
1
x 1
38.
2
1
x x 1
39.
3
x
2 x2
40 -8
41. 1
x 2
Trang 340. Y 2x 12 32x 2 1 2x2
2x x 1 4x 2x x
x 1 x x 1 x 1
2x 2x 1 2x 4x
2x y 8y 2x y D
2x xy y 4x 2x xy
45.
x 1 x 3x 1 1 x 1
x x 1 x 1 x 1 1 x
x 16 x 4x x 4x 4 x
47.
2
2
x 2 2x 3x 3 4x x 7
x 1 x 1 x x x
48.
2
x 1 x 1 x x 1 x 1 x 2 x 2x
x y 2x 2y 2x y x
50.
3
2 2 : 9
3 3 3 3
2
2
2
x
x x
x x
x x
x
52.
1
2 1
3 1 1
1
2
3 2
3 4
x
x x
x x
x x x
x x x
x A
2
1 : 2
2 6
2
2
5
1
1 1
1 1
2 2 3
2 6
56. 7 152 2 113 31 2 2 33
x
x x
x x
x
x
A
2
3 3
2 6
4 : 2
1 1
2 8
x
x x
x x
x x
A
x
2003 x
1 x
1 x x 1 x
1 x 1 x
1 x
2
2
:
x y x y x y x y 2xy
42. 3
x 1
43. 1 2x
44.
4x 2y
x 2x y
45.
2
1
x x 1
46 -1
47. x 1 x
48. 1 x
49 1
50. 3
x2
51. 3
x 3
52.
2
x x 1
x 1
53.
2
2x 4x 2 x
54. 2
x 2
55.
2
x
x x 1
56
57.
58. x 2003
x
59. x y
x y
60. 2
x 3
61.
x 3
x 1
Trang 460. T= 1 1 2 (1 2 )
( 1) 1 1
62.
:
A
63.
2 :
A
:
x B
2
y 1 3 y 11 y
y 3 y 1 y 2y 3
2
x 2 x 1 x 5
x 1 x 2 x x 2
x 2 2 x 4 x 2 4x 8
2
2 x 2x 1
x 1 x 1
70.
2
x 1 x 1 x 1 F
2 2x x 1 x 1
2 x 4 x x 2x x
a ab ba b
x 1 x x x 1 x 1
74.
2
a 2 a 1 a 1 a 1 a 1
2x 3 2x 3 2 9 4x
1 4x 2x x
x 1 x x 2 x 1
62. 4x
x 3
63. 2
x y xy
64 -5xy
65. 2
7y 7y7
66. 2
5x 5x5
67. 1 2
68. 3x 2
69. x 1
x 1
70.
2
1 x x
71.
2
4x
x 3
72. 2 2
b a
73. 1
x 1
74.
2
a 1 2a
75.
1
2 2x 3
76.
2
2x 1 2x x
77. x 2 3x
Trang 578. A 22x 2 2x x :x 2x
x 3x x 4x 3 x 1 x 3
x 2 x 2 4 x x 3
80.
2
2
1 x 1 2x x x x
3 x 3 x 9 x x 3
81.
2
5 4 3x 51x 15
82.
2
x 2x 1 x 1 x 2x 1 5x 5
83.
4 2
x 2x 2 x x 4x x 2x
85.
2
4x 3x 17 2x 1 6x x 3
x 1 x x 1 x x x x 1
x 9y x 3xy x 3y
87.
2
x 1 x x 1 x x x x 1
88.
2
x 1 x (x 1) x 1 x x 1
89.
2
2
x 9 3 x x 3 x 3
5x 20 x 8x 16 6x 29
91.
2
8x 18 2x 3x 4x 6 9 4x
2x 3x 2x 3 9 4x 6x 9
2x 2x 1 2x 4x x
94.
x 2006x 2009 x 2008 x 3x
78. 1 x
79. x 2
x 3
80. 10
3 x
81. 1 2x
82.
2
x 1
83. 2
x 1
84. x
x 2
85. 12
x 3
86. 1 x
87. 12
1 x
88. 5
x 2
89. 6
x2
90. x
x 4
91. 1 x
92. 6
x 2
93. 1
x 3
94. 1
x3