1. 先化简求值:2(3a2﹣ab)﹣3(2a2﹣ab)中a﹣2b3.
2.先化简求值:6a2b﹣(﹣3a2b+5ab2)﹣2(5a2b﹣3ab2)中.
3.先化简求值:3x2y2﹣[5xy2﹣(4xy2﹣3)+2x2y2]中x﹣3y2.
4.先化简求值:5ab2+3a2b﹣3(a2b﹣ab2)中a2b﹣1.
5.先化简求值:2x2﹣y2+(2y2﹣x2)﹣3(x2+2y2)中x3y﹣2.
6.先化简求值:﹣x2﹣(3x﹣5y)+[4x2﹣(3x2﹣x﹣y)]中.
7.先化简求值:5x2﹣[x2+(5x2﹣2x)﹣2(x2﹣3x)]中x.
8.先化简求值:(6a2﹣6ab﹣12b2)﹣3(2a2﹣4b2)中a﹣b﹣8.
9.先化简求值中a﹣2.
10.化简求值:(﹣3x2﹣4y)﹣(2x2﹣5y+6)+(x2﹣5y﹣1)中xy满足|x﹣y+1|+(x﹣5)20.
11.先化简求值:(1)5a2b﹣2ab2+3ab2﹣4a2b中a﹣1b2
(2)(2x3﹣xyz)﹣2(x3﹣y3+xyz)﹣(xyz+2y3)中x1y2z﹣3.
12.先化简求值:x2y﹣(2xy﹣x2y)+xy中x﹣1y﹣2.
13.已知:|x﹣2|+|y+1|0求5xy2﹣2x2y+[3xy2﹣(4xy2﹣2x2y)]值.
14.先化简求值:﹣9y+6x2+3(y﹣x2)中x﹣2y﹣.
15.设A2x2﹣3xy+y2+2x+2yB4x2﹣6xy+2y2﹣3x﹣y|x﹣2a|+(y﹣3)20B﹣2Aa求a值.
16.已知M﹣xy2+3x2y﹣1N4x2y+2xy2﹣x
(1)化简:4M﹣3N (2)x﹣2y1时求4M﹣3N值.
17 求代数式值:(1)(5x2﹣3x)﹣2(2x﹣3)+7x2中x﹣2 (2)2a﹣[4a﹣7b﹣(2﹣6a﹣4b)]中ab.
18.先化简求值:5(xy+3x2﹣2y)﹣3(xy+5x2﹣2y)中xy﹣1.
19. 化简:(1)(9y﹣3)+2(y﹣1) (2)求x﹣2(x﹣y2)+(﹣x+y2)值中x﹣2y.
20.先化简求值:(5a+2a2﹣3+4a3)﹣(﹣a+4a3+2a2)中a1.
21.|a|3ba﹣2时化简代数式1﹣{a﹣b﹣[a﹣(b﹣a)+b]}求代数式值.
22.先化简求值:a2﹣(2a2+2ab﹣b2)+(a2﹣ab﹣b2)中a3b﹣2.
23.先化简求值:3a2﹣(2ab+b2)+(﹣a2+ab+2b2)中a﹣1b2.
24.化简求值:3a2b﹣〔2ab2﹣2(ab﹣a2b)+ab〕+3ab2中a3b﹣.
25.已知3xa﹣2y2z3﹣4x3yb﹣1z3类项求3a2b﹣[2ab2﹣2(a2b+2ab2)]值.
26.先化简求值:﹣8xy2+3xy﹣2(xy2﹣xy)中xy﹣2.
27.已知A3x2+3y2﹣5xyB2xy﹣3y2+4x2求:
(1) 2A﹣B
(2)时2A﹣B值.
28.先化简计算:2(a2b+ab2)﹣[2ab2﹣(1﹣a2b)]﹣2中a﹣2b.
29.先化简求值:2(a2﹣2ab)﹣3(a2+2ab)中a﹣1b2.
30.已知A4(2﹣x2)﹣2xB2x2﹣x+3.
(1)x时求A﹣2B值
(2)A2B互相反数求x值.
31.先化简求值已知a﹣2b﹣1c3求代数式5abc﹣2a2b﹣[(4ab2﹣a2b)﹣3abc]值.
32.化简(求值)2(x2y+xy2)﹣2(x2y﹣x)﹣2xy2﹣2y值中x﹣2y2.
33.先化简求值:﹣2(ab﹣3a2)﹣[a2﹣5(ab﹣a2)+6ab]中a2b﹣3.
34.先化简求值:3a3﹣[a3﹣3b+(6a2﹣7a)]﹣2(a3﹣3a2﹣4a+b)中a2b﹣1
35.先化简求值:(5a2b+4b3﹣2ab2+3a3)﹣(2a3﹣5ab2+3b3+2a2b)中a﹣2b3.
36.先化简求值中a1b﹣2.
37.先化简求值:(a2﹣3ab﹣2b2)﹣(a2﹣2b2)中b﹣8.
38.化简:中x.
39.化简求值:3(x3﹣2y2﹣xy)﹣2(x3﹣3y2+xy)中x3y1.
40.先化简求值:3x2y﹣[2xy2﹣2(xy﹣x2y)+xy]+3xy2中xy﹣5.
41.先化简求值:8mn﹣[4m2n﹣(6mn2+mn)]﹣29mn2中m﹣1n.
42.先化简求值:4ab﹣3b2﹣[(a2+b2)﹣(a2﹣b2)]中a1b﹣3.
43.先化简求值:3x2+4x﹣2x2﹣2(x2+2x﹣1)﹣x+1中x﹣2.
44.化简求值:(2x2﹣x﹣1)﹣(x2﹣x﹣)+(3x2﹣3)中x.
45.化简求值:3(x2﹣xy)﹣5()中x﹣2y﹣3.
46.先化简求值:9(xy﹣x2y)﹣2(xy﹣x2y﹣1)中xy+10.
47.先化简求值:4(3x2y﹣xy2)﹣2(xy2+3x2y)中xy﹣1.
48.已知x﹣3y﹣求代数式值.
49.先化简求值:4xy﹣(2x2+5xy﹣y2)+2(x2+3xy)中x﹣2y1.
50.先化简求值:(8xy﹣3x2)﹣5xy﹣3(xy﹣2x2+3)中.
51.先化简求值:中.
52.先化简求值:3a2﹣7a+[3a﹣2(a2﹣2a﹣1)]中a﹣2.
53.先化简﹣x2﹣(3x﹣5y)+[4x2﹣(3x2﹣x﹣y)]求值中xy.
54.先化简求值:中x﹣2.
55.先化简求值:3()﹣(5x2y﹣4xy2)中x2y﹣1.
56.先化简求值已知a1b﹣求项式值.
57.先化简求值:3(x2﹣xy)﹣(4x2﹣3xy﹣1)中.
58.先化简求值:中.
59.先化简求值:2(x2y﹣xy2﹣1)﹣(2x2y﹣xy2﹣y)中x2y﹣1.
60.先化简求值:(2m2n+2mn2)﹣2(m2n﹣1)﹣3+mn中.
61.先化简求值.3x﹣5(x﹣2xy2)+8(x﹣3xy2)中.
62.先化简求值:中x﹣2.
63.先化简求值:﹣5x2y﹣[3x2y﹣2(xy2﹣x2y)].中x2y﹣1.
64.先化简求值:中y2008.
65.先化简求值:5a2﹣3b2+[﹣(a2﹣2ab﹣b2)﹣(5a2+2ab+3b2)]中a1b﹣.
66.先化简求值:2x2+3x+5+[4x2﹣(5x2﹣x+1)]中x3.
67.先简化求值: (中x﹣2y)
68.先化简求值.2(a2b+2b3﹣ab2)+3a3﹣(2a2b﹣3ab2+3a3)﹣4b3中a﹣3b2.
69.先化简求值:2(a2b+ab3)﹣3(a2b﹣3)﹣2ab3﹣1中a2b﹣2.
70.已知ab满足等式求代数式值.
71.先化简求值4xy﹣[2(x2+xy﹣2y2)﹣3(x2﹣2xy+y2)]中x﹣y
72.先化简求值:2x2+(﹣x2+3xy+2y2)﹣( x2﹣xy+2y2)中 xy3.
73.先化简求值:(2x2﹣5xy)﹣3(x2﹣y2)+x2﹣3y2中x﹣3y.
74.先化简求值:5a2b+3b2﹣2(3a2b+ab2)+(4a2b﹣3b2)中a﹣2b1.
75.先化简求值:5a﹣[a2+(5a2﹣3a)﹣6(a2﹣2a)]中a﹣.
76.先化简求值:3x2y﹣[2xy2﹣4(xy﹣x2y)+xy]+3xy2中x3y﹣1.
77.先化简求值:2(a2b+ab2)﹣3(a2b﹣3)﹣2ab2﹣1.中a﹣2b2.
78.先化简求值:中x3y.
79.化简求值:x﹣2(3y2﹣2x)﹣4(2x﹣y2)中|x﹣2|+(y+1)20.
80.先化简求值5x2﹣(3y2+5x2﹣2xy)+(﹣7xy+4y2)中:x﹣1y﹣.
81.先化简求值:中xy满足(x﹣2)2+|y+3|0.
82.先化简求值:2(x2﹣3xy﹣y2)﹣(2x2﹣7xy﹣2y2)中x4y﹣1时.
83.求代数式值:2(3xy+4x2)﹣3(xy+4x2)中x﹣3.
84.先化简求值:5(a2b﹣ab2)﹣(ab2+3a2b)中
85. 先化简求值:5(3a2b﹣ab2)﹣(ab2+3a2b)﹣4(3a2b﹣ab2)中a﹣2b.
86.先化简求值:(a2b﹣2ab2﹣b3)÷b+(b﹣a)(b+a)中a﹣b2012.
87.先化简求值:中.
88.先化简求值:4m3﹣(3m2+5m﹣2)+2(3m+m2﹣2m3)﹣1中m2011.
89.先化简求值 2(3x2﹣x+4)﹣3(2x2﹣2x+3)中.
90.先化简求值.2(2xy2﹣y2)﹣(4xy2+y2﹣x2y)﹣y2中xy﹣.
整式化简求值90题参考答案:
1.原式6a2﹣2ab﹣6a2+3abab
a﹣2b3时原式ab﹣2×3﹣6.
2.原式6a2b+3a2b﹣5ab2﹣10a2b+6ab2﹣a2b+ab2a﹣2b代入式:
原式﹣(﹣2)2×+(﹣2)×2﹣2﹣﹣2.
3.原式3x2y2﹣5xy2+4xy2﹣3﹣2x2y2
x2y2﹣xy2﹣3
∴x﹣3y2时原式45
4.原式5ab2+3a2b﹣3a2b+2ab2(4分)
7ab2.(6分)
a2b﹣1时
原式7×2×(﹣1)2(7分)
14.
5.原式2x2﹣y2+2y2﹣x2﹣3x2﹣6y2﹣2x2﹣5y2.
x3y﹣2时
原式﹣18﹣20﹣38.
6.﹣x2﹣(3x﹣5y)+[4x2﹣(3x2﹣x﹣y)]
﹣x2﹣3x+5+[4x2﹣3x2+x+y]
﹣2x+6y
时原式﹣3
7.原式5x2﹣(x2+5x2﹣2x﹣2x2+6x)
x2﹣4x
x时式
8.原式6a2﹣6ab﹣12b2﹣6a2+12b2﹣6ab
a﹣b﹣8时
原式﹣6×(﹣)×(﹣8)﹣24.
9.
﹣a2﹣9a+7
a﹣2时
原式﹣(﹣2)2﹣9×(﹣2)+7
﹣4+18+7
21.
10.∵|x﹣y+1|+(x﹣5)20
x﹣y+10x﹣50
解x5y6.
(﹣3x2﹣4y)﹣(2x2﹣5y+6)+(x2﹣5y﹣1)
﹣3x2﹣4y﹣2x2+5y﹣6+x2﹣5y﹣1
﹣4x2﹣4y﹣7
﹣100﹣24﹣7
﹣131
11.(1)原式a2b+ab2
a﹣1b2时
原式(﹣1)2×2+(﹣1)×22
﹣2
(2)原式2x3﹣xyz﹣2x3+2y3﹣2xyz﹣xyz﹣2y3
﹣4xyz
x1y2z﹣3时
原式﹣4×1×2×(﹣3)24
12.原式x2y﹣2xy+x2y+xy2x2y﹣xy
x﹣1y﹣2时
原式2×(﹣1)2×(﹣2)﹣(﹣1)×(﹣2)﹣6.
13.∵|x﹣2|+|y+1|0
∴x﹣20y+10
解x2y﹣1
原式5xy2﹣2x2y+3xy2﹣4xy2+2x2y
4xy2
4×2×1
8
14.原式﹣9y+6x2+3y﹣3x23x2﹣6y
x﹣2y﹣:原式12+214
15.∵|x﹣2a|+(y﹣3)20
∴x2ay3
∵B﹣2A4x2﹣6xy+2y2﹣3x﹣y﹣2(2x2﹣3xy+y2+2x+2y)
4x2﹣6xy+2y2﹣3x﹣y﹣4x2+6xy﹣2y2﹣4x﹣4y
﹣7x﹣5y
B﹣2Aa
∴﹣7×2a﹣5×3a
∴a﹣1
16.(1)4M﹣3N4(﹣xy2+3x2y﹣1)﹣3(4x2y+2xy2﹣x)
﹣4xy2+12x2y﹣4﹣12x2y﹣6xy2+3x
﹣10xy2+3x﹣4
(2)x﹣2y1时
4M﹣3N﹣10×(﹣2)×1+3×(﹣2)﹣4
20﹣6﹣4
10.
17.(1)原式(5x2﹣3x)﹣2(2x﹣3)+7x212x2﹣7x+6
x﹣2时原式12×(﹣2)2﹣7×(﹣2)+668
(2)原式2a﹣[4a﹣7b﹣2+6a+4b]
2a﹣[10a﹣3b﹣2]
﹣8a+3b+2
ab时原式6
18.原式5xy+15x2﹣10y﹣3xy﹣15x2+6y2xy﹣4y
xy﹣1时原式2××(﹣1)﹣4×(﹣1)3.
19.(1)原式3y﹣1+2y﹣2
5y﹣3
(2)原式x﹣2x+y2﹣x+y2
﹣3x+y2
x﹣2y时原式﹣3×(﹣2)+()26+
6
20.(5a+2a2﹣3+4a3)﹣(﹣a+4a3+2a2)
5a+2a2﹣3+4a3+a﹣4a3﹣2a2
(5a+a)+(2a2﹣2a2)﹣3+(4a3﹣4a3)
6a﹣3
a1时
原式6×1﹣3
6﹣3
3
21.化简代数式原式1+a+b
a3时b1代数式值5
a﹣3时b﹣5代数式值﹣7.
22.a2﹣(2a2+2ab﹣b2)+(a2﹣ab﹣b2)
a2﹣2a2﹣2ab+b2+a2﹣ab﹣b2
﹣a2﹣3ab.
a3b﹣2时
原式﹣×32﹣3×3×(﹣2)
﹣3+18
15
23.原式2a2﹣ab+b2中a﹣1b2.2a2﹣ab+b28
24.原式3a2b﹣(2ab2﹣2ab+3a2b+ab)+3ab2ab2+ab
a3b﹣代入原式ab2+ab﹣
25 ∵3xa﹣2y2z3﹣4x3yb﹣1z3类项
∴a﹣23b﹣12
∴a5b3.
3a2b﹣[2ab2﹣2(a2b+2ab2)]
3a2b﹣[2ab2﹣2a2b﹣4ab2]
3a2b﹣2ab2+2a2b+4ab2
5a2b+2ab2a5b3时
原式5×52×3+2×5×32465.
26.﹣8xy2+3xy﹣2(xy2﹣xy)
﹣8xy2+3xy﹣2xy2+2xy
﹣10xy2+5xy.
xy﹣2时
原式﹣10xy2+5xy
﹣10××(﹣2)2+5××(﹣2)
﹣8﹣2
﹣10
27.(1)2A﹣B2(3x2+3y2﹣5xy)﹣(2xy﹣3y2+4x2)
6x2+6y2﹣10xy﹣2xy+3y2﹣4x22x2+9y2﹣12xy
(2)时
2A﹣B2x2+9y2﹣12xy31
28 原式2a2b+2ab2﹣2ab2+1﹣a2b﹣2
a2b﹣1
a﹣2b时
∴原式a2b﹣1(﹣2)2×﹣12﹣11.
29.2(a2﹣2ab)﹣3(a2+2ab)
2a2﹣4ab﹣3a2﹣6ab
﹣a2﹣10ab
a﹣1b2时
原式﹣(﹣1)2﹣10×(﹣1)×2
﹣1+20
19.
30.(1)A4(2﹣x2)﹣2xB2x2﹣x+3.
A﹣2B4(2﹣x2)﹣2x﹣2(2x2﹣x+3)
﹣8x2+2
x时A﹣2B﹣8×()2+2
(2)A4(2﹣x2)﹣2xB2x2﹣x+3:2B4x2﹣2x+6
A2B互相反数:A+2B0
4(2﹣x2)﹣2x+4x2﹣2x+60
4x14
解:x
x值:.
31.原式5abc﹣2a2b﹣4ab2+a2b+3abc8abc﹣a2b﹣4ab2
a﹣2b﹣1c3时原式8×2×1×3﹣4×(﹣1)﹣4×(﹣2)×160.
32.2(x2y+xy2)﹣2(x2y﹣x)﹣2xy2﹣2y
2x2y+2 xy2﹣2x2y+2x﹣2xy2﹣2y
2x﹣2y
x﹣2y2代入式
原式2×(﹣2)﹣2×2﹣8
33.原式﹣2ab+6a2﹣(a2﹣5ab+5a2+6ab)
﹣2ab+6a2﹣a2+5ab﹣5a2﹣6ab
﹣3ab
a2b﹣3时原式﹣3×2×(﹣3)18
34.原式3a3﹣[a3﹣3b+6a2﹣7a]﹣2a3+6a2+8a﹣2b
3a3﹣a3+3b﹣6a2+7a﹣2a3+6a2+8a﹣2b
15a+b
a2b﹣1时
原式15×2﹣129.
35.原式5a2b+4b3﹣2ab2+3a3﹣2a3+5ab2﹣3b3﹣2a2b
a3+3a2b+3ab2+b3
a﹣2b3时
原式(﹣2)3+3×(﹣2)2×3+3×(﹣2)×32+33﹣8+36﹣54+27
1.
36.
a﹣2ab﹣2b2a+2ab+b2
(+)a+(﹣2+2)ab+(﹣2+1)b2
2a+0﹣b2
2a﹣b2
a1b﹣2代入式
式2×1﹣(﹣2)2
2﹣4
﹣2.
37.原式a2﹣3ab﹣2b2﹣a2+2b2(3分)
﹣3ab
b﹣8时
原式﹣3×()×(﹣8)(7分)
﹣12.
38.原式2x2﹣05+3x﹣4x+4x2﹣2+x+25
6x2
x时原式6×.
39.原式3x3﹣6y2﹣3xy﹣3x3+6y2﹣2xy
﹣5xy
x3y1时原式﹣5×3×1﹣15.
40.原式3x2y﹣[2xy2﹣(2xy﹣3x2y)+xy]+3xy2
3x2y﹣(2xy2﹣2xy+3x2y+xy)+3xy2
3x2y﹣2xy2+2xy﹣3x2y﹣xy+3xy2
xy+xy2
xy﹣5时
原式×(﹣5)+×25.
41.原式8mn﹣[4m2n﹣6mn2﹣mn]﹣29mn28mn﹣4m2n+6mn2+mn﹣29mn29mn﹣4m2n﹣23mn2m﹣1n时
原式9×(﹣1)×﹣4×12×﹣23×(﹣1)×
﹣﹣2+
﹣.
42.原式4ab﹣3b2﹣2b2
4ab﹣5b2
a1b﹣3时
原式4×1×(﹣3)﹣5×(﹣3)2
﹣57.
43.原式3x2+4x﹣2x2﹣2x2﹣4x+2﹣x+1
﹣x2﹣x+3
x﹣2时原式﹣(﹣2)2﹣(﹣2)+31
44.(2x2﹣x﹣1)﹣(x2﹣x﹣)+(3x2﹣3)
2x2﹣x﹣1﹣x2+x++3x2﹣3
4x2﹣4
x原式1﹣4﹣3.
45.原式3x2﹣3xy﹣3x2+5xy
2xy
x﹣2y﹣3时原式2×(﹣2)×(﹣3)12.
46.原式3xy﹣x2y﹣2xy+x2y+2…(1分)
xy+2…(2分)
∵xy+10∴xy﹣1…(3分)
∴原式﹣1+21…(4
47.原式12x2y﹣4xy2﹣2xy2﹣6x2y
6x2y﹣6xy2
xy﹣1时
原式6x2y﹣6xy26xy(x﹣y)6×(﹣)×(+1)
﹣4.
48.原式x2﹣y﹣x2﹣y﹣x2﹣y
x﹣3y﹣时
原式﹣×(﹣3)2﹣(﹣)﹣3+﹣.
49.原式4xy﹣2x2﹣5xy+y2+2x2+6xy)
5xy+y2.
x﹣2y1时原式5×(﹣2)+1﹣9.
50.(8xy﹣3x2)﹣5xy﹣3(xy﹣2x2+3)
8xy﹣3x2﹣5xy﹣3xy+6x2﹣9
3x2﹣9
时原式
51.原式x2﹣[7x﹣2x+﹣2x2]+
x2﹣7x+2x﹣+2x2+
3x2﹣5x
x﹣时原式3×(﹣)2+5×+.
52.3a2﹣7a+[3a﹣2(a2﹣2a﹣1)]
3a2﹣7a+3a﹣2a2+4a+2
a2+2
d﹣2时原式4+48.
53.﹣x2﹣(3x﹣5y)+[4x2﹣(3x2﹣x﹣y)]﹣x2﹣3x+5y+[4x2﹣3x2+x+y]﹣x2﹣3x+5y+4x2﹣3x2+x+y﹣2x+6y.
xy时原式﹣2×+6×1
54.原式x﹣x+y2﹣x+y2﹣2x+y2
x2y时原式﹣2×2+()2﹣4+﹣.
55.原式x2y﹣3xy2﹣5x2y+4xy2
﹣x2y+xy2
x2y﹣1时
原式﹣×22×(﹣1)+2×(﹣1)2
16
56.
a3﹣2b3+2ab2﹣a2b﹣2ab2+2b3
a3﹣a2b
a1b﹣代入:
原式13﹣12×
1+
.
57.原式3x2﹣3xy﹣4x2+3xy+1
﹣x2+1
x2y﹣3时原式﹣22+1﹣3.
58.原式9x+6x2﹣3x+2x2﹣6x+6
8x2+6
x﹣时原式8×(﹣)2+62+68.
59.原式2x2y﹣2xy2﹣2﹣2x2y+xy2+y﹣xy2+y﹣2
x2y﹣1时原式﹣2×(﹣1)2﹣1﹣2﹣2﹣1﹣2﹣5.
60.原式2m2n+2mn2﹣2m2n+2﹣3+mn
2mn2+mn﹣1
m﹣2n时原式2×(﹣2)×()2+(﹣2)×﹣1﹣3
61.3x﹣5(x﹣2xy2)+8(x﹣3xy2)3x﹣5x+10xy2+8x﹣24xy26x﹣14xy2
x4y﹣时
原式6×4﹣14×4×(﹣)224﹣126﹣102.
62.(2x2﹣x+1)﹣4(x﹣x2+)2x2﹣x+1﹣4x+4x2﹣26x2﹣x﹣1
x﹣2时原式6×(﹣2)2﹣×(﹣2)﹣124+9﹣132
63.原式﹣5x2y﹣3x2y+2xy2﹣2x2y2xy2
x2y﹣1时原式2×2×(﹣1)24.
答案4
64.原式﹣x2+x﹣2y+x+2y﹣x2+x
xy2008时原式﹣()2+×﹣+.
65.原式5a2﹣3b2﹣a2+2ab+b2﹣5a2﹣2ab﹣3b2
﹣a2﹣5b2
a1b﹣时原式﹣1﹣5×﹣
66.原式2x2+3x+5+[4x2﹣5x2+x﹣1]
2x2+3x+5+4x2﹣5x2+x﹣1
2x2+4x2﹣5x2+3x+x+5﹣1
x2+4x+4
∵x3
∴x2+4x+49+12+4
25.
67.原式x2﹣xy+y2﹣x2+xy﹣y2﹣x2﹣xy
x﹣2y时原式﹣2+﹣1.
68.原式2a2b+4b3﹣2ab2+3a3﹣2a2b+3ab2﹣3a3﹣4b3ab2
a﹣3b2时原式﹣3×22﹣12.
69.原式2a2b2ab3﹣3a2b+9﹣2ab3﹣1
2a2b﹣3a2b+2ab3﹣2ab3+9﹣1
﹣a2b+8
∵a2b﹣2
∴﹣a2b+88+816
70.∵
∴a+03b+20
∴a﹣b﹣
a﹣b+a+b﹣a+b+a+b﹣a+b
(+﹣+﹣)a+(﹣++++)b
a+b
×(﹣)+×(﹣)
﹣.
71.∵4xy﹣[2(x2+xy﹣2y2)﹣3(x2﹣2xy+y2)]
4xy﹣(2x2+2xy﹣4y2﹣3x2+6xy﹣3y2)
x2﹣4xy+7y2
∴x﹣y时
原式x2﹣4xy+7y2(﹣)2﹣4×(﹣)×+7×()2+1+3
72.原式2x2﹣x2+3xy+2y2﹣x2+xy﹣2y2
(2﹣1﹣1)x2+(3+1)xy+(2﹣2)y2
4xy
xy3时原式4××36
73.原式2x2﹣5xy﹣3x2+3y2+x2﹣3y2(2﹣3+1)x2+(3﹣3)y2﹣5xy
﹣5xy
x﹣3y时原式(﹣5)×(﹣3)×5
74.原式5a2b+3b2﹣6a2b﹣2ab2+4a2b﹣3b23a2b﹣2ab2
a﹣2b1时原式12+416.
75.原式5a﹣a2﹣5a2+3a+6a2﹣12a8a﹣12
a﹣时原式﹣2﹣12﹣14.
76.原式3x2y﹣[2xy2﹣2xy+3x2y+xy]+3xy23x2y﹣2xy2+xy﹣3x2y+3xy2xy2+xy
x3y﹣1代入:原式xy2+xy0
77.2(a2b+ab2)﹣3(a2b﹣3)﹣2ab2﹣1
2a2b+2ab2﹣3a2b+9﹣2ab2﹣1
﹣a2b+8
a﹣2b2时
原式﹣(﹣2)2×2+80.
78.原式﹣3x+5y2﹣+
﹣4x+y2
x3y时原式(﹣4)×3+×()20.
79.∵|x﹣2|+(y+1)20
∴x2y﹣1
x﹣2(3y2﹣2x)﹣4(2x﹣y2)x﹣6y2+4x﹣8x+4y2﹣3x﹣2y2
x2y﹣1时原式﹣6﹣2﹣8.
80.原式5x2﹣3y2﹣5x2+2xy﹣7xy+4y2﹣5xy+y2
x﹣1y﹣时原式﹣5×(﹣1)×(﹣)+(﹣)2﹣+﹣.
81.原式﹣3x+y2
(x﹣2)2+|y+3|0
知x﹣20y+30
解x2y﹣3
代入化简结果原式﹣3×2+(﹣3)23
82.原式x2﹣6xy﹣2y2﹣2x2+7xy+2y2﹣x2+xy
x4y﹣1时
原式﹣42+4×(﹣1)﹣20
83.∵原式5a2b﹣5ab2﹣ab2﹣3a2b
2a2b﹣6ab2
∴时
原式.
84.∵原式5a2b﹣5ab2﹣ab2﹣3a2b
2a2b﹣6ab2
∴时
原式.
85.原式15a2b﹣5ab2﹣ab2﹣3a2b﹣12a2b+4ab2﹣2ab2
a﹣2b时原式﹣2×(﹣2)×1
86.原式a2﹣2ab﹣b2+b2﹣a2﹣2ab
a﹣b2012时原式﹣2×(﹣)×20122012.
87.原式2x﹣y﹣6x+y﹣4x
x﹣y2010时原式﹣4×(﹣)1.
88.原式6x2﹣2x+8﹣6x2+6x﹣94x﹣1
时原式﹣7.
89.原式6x2﹣2x+8﹣6x2+6x﹣94x﹣1
时原式﹣7.
90.原式4xy2﹣y2﹣4xy2﹣y2+x2y﹣y2﹣3y2+x2y.
xy﹣时原式﹣3×(﹣)2+()2×(﹣)
.
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