整式的加减化简求值专项练习90题(有答案)
1.先化简再求值:2(3a2﹣ab)﹣3(2a2﹣ab),其中a=﹣2,b=3.
2.先化简再求值:6a2b﹣(﹣3a2b+5ab2)﹣2(5a2b﹣3ab2),其中.
3.先化简,再求值:3x2y2﹣[5xy2﹣(4xy2﹣3)+2x2y2],其中x=﹣3,y=2.
4.先化简,再求值:5ab2+3a2b﹣3(a2b﹣ab2),其中a=2,b=﹣1.
5.先化简再求值:2x2﹣y2+(2y2﹣x2)﹣3(x2+2y2),其中x=3,y=﹣2.
6.先化简,再求值:﹣x2﹣(3x﹣5y)+[4x2﹣(3x2﹣x﹣y)],其中.
7.先化简,再求值:5x2﹣[x2+(5x2﹣2x)﹣2(x2﹣3x)],其中x=.
8.先化简,再求值:(6a2﹣6ab﹣12b2)﹣3(2a2﹣4b2),其中a=﹣,b=﹣8.
9.先化简,再求值,其中a=﹣2.
10.化简求值:(﹣3x2﹣4y)﹣(2x2﹣5y+6)+(x2﹣5y﹣1),其中x、y满足|x﹣y+1|+(x﹣5)2=0.
11.先化简,再求值:(1)5a2b﹣2ab2+3ab2﹣4a2b,其中a=﹣1,b=2;
(2)(2x3﹣xyz)﹣2(x3﹣y3+xyz)﹣(xyz+2y3),其中x=1,y=2,z=﹣3.
12.先化简,再求值:x2y﹣(2xy﹣x2y)+xy,其中x=﹣1,y=﹣2.
13.已知:|x﹣2|+|y+1|=0,求5xy2﹣2x2y+[3xy2﹣(4xy2﹣2x2y)]的值.
14.先化简,再求值:﹣9y+6x2+3(y﹣x2),其中x=﹣2,y=﹣.
15.设A=2x2﹣3xy+y2+2x+2y,B=4x2﹣6xy+2y2﹣3x﹣y,若|x﹣2a|+(y﹣3)2=0,且B﹣2A=a,求a的值.
16.已知M=﹣xy2+3x2y﹣1,N=4x2y+2xy2﹣x
(1)化简:4M﹣3N;
(2)当x=﹣2,y=1时,求4M﹣3N的值.
17.求代数式的值:(1)(5x2﹣3x)﹣2(2x﹣3)+7x2,其中x=﹣2;
(2)2a﹣[4a﹣7b﹣(2﹣6a﹣4b)],其中a=,b=.
18.先化简,再求值:5(xy+3x2﹣2y)﹣3(xy+5x2﹣2y),其中x=,y=﹣1.
19.化简:(1)(9y﹣3)+2(y﹣1)
(2)求x﹣2(x﹣y2)+(﹣x+y2)的值,其中x=﹣2,y=.
20.先化简,再求值:(5a+2a2﹣3+4a3)﹣(﹣a+4a3+2a2),其中a=1.
21.当|a|=3,b=a﹣2时,化简代数式1﹣{a﹣b﹣[a﹣(b﹣a)+b]}后,再求这个代数式的值.
22.先化简,再求值:a2﹣(2a2+2ab﹣b2)+(a2﹣ab﹣b2),其中a=3,b=﹣2.
23.先化简再求值:3a2﹣(2ab+b2)+(﹣a2+ab+2b2),其中a=﹣1,b=2.
24.化简求值:3a2b﹣〔2ab2﹣2(ab﹣a2b)+ab〕+3ab2,其中a=3,b=﹣.
25.已知3xa﹣2y2z3和﹣4x3yb﹣1z3是同类项,求3a2b﹣[2ab2﹣2(a2b+2ab2)]的值.
26.先化简,再求值:﹣8xy2+3xy﹣2(xy2﹣xy),其中x=,y=﹣2.
27.已知,A=3x2+3y2﹣5xy,B=2xy﹣3y2+4x2,求:
(1)
2A﹣B;
(2)当时,2A﹣B的值.
28.先化简,后计算:2(a2b+ab2)﹣[2ab2﹣(1﹣a2b)]﹣2,其中a=﹣2,b=.
29.先化简,再求值:2(a2﹣2ab)﹣3(a2+2ab),其中a=﹣1,b=2.
30.已知A=4(2﹣x2)﹣2x,B=2x2﹣x+3.
(1)当x=时,求A﹣2B的值;
(2)若A与2B互为相反数,求x的值.
31.先化简再求值,已知a=﹣2,b=﹣1,c=3,求代数式5abc﹣2a2b﹣[(4ab2﹣a2b)﹣3abc]的值.
32.化简(求值)2(x2y+xy2)﹣2(x2y﹣x)﹣2xy2﹣2y的值,其中x=﹣2,y=2.
33.先化简,再求值:﹣2(ab﹣3a2)﹣[a2﹣5(ab﹣a2)+6ab],其中a=2,b=﹣3.
34.先化简,再求值:3a3﹣[a3﹣3b+(6a2﹣7a)]﹣2(a3﹣3a2﹣4a+b)其中a=2,b=﹣1,35.先化简,再求值:(5a2b+4b3﹣2ab2+3a3)﹣(2a3﹣5ab2+3b3+2a2b),其中a=﹣2,b=3.
36.先化简,再求值,其中a=1,b=﹣2.
37.先化简再求值:(a2﹣3ab﹣2b2)﹣(a2﹣2b2),其中,b=﹣8.
38.化简:,其中x=.
39.化简求值:3(x3﹣2y2﹣xy)﹣2(x3﹣3y2+xy),其中x=3,y=1.
40.先化简再求值:3x2y﹣[2xy2﹣2(xy﹣x2y)+xy]+3xy2,其中x=,y=﹣5.
41.先化简,再求值:8mn﹣[4m2n﹣(6mn2+mn)]﹣29mn2,其中m=﹣1,n=.
42.先化简,再求值:4ab﹣3b2﹣[(a2+b2)﹣(a2﹣b2)],其中a=1,b=﹣3.
43.先化简,再求值:3x2+4x﹣2x2﹣2(x2+2x﹣1)﹣x+1,其中x=﹣2.
44.化简求值:(2x2﹣x﹣1)﹣(x2﹣x﹣)+(3x2﹣3),其中x=.
45.化简求值:3(x2﹣xy)﹣5(),其中x=﹣2,y=﹣3.
46.先化简,再求值:9(xy﹣x2y)﹣2(xy﹣x2y﹣1)其中xy+1=0.
47.先化简,再求值:4(3x2y﹣xy2)﹣2(xy2+3x2y),其中x=,y=﹣1.
48.已知x=﹣3,y=﹣,求代数式的值.
49.先化简,再求值:4xy﹣(2x2+5xy﹣y2)+2(x2+3xy),其中x=﹣2,y=1.
50.先化简,再求值:(8xy﹣3x2)﹣5xy﹣3(xy﹣2x2+3),其中.
51.先化简,再求值:,其中.
52.先化简,再求值:3a2﹣7a+[3a﹣2(a2﹣2a﹣1)],其中a=﹣2.
53.先化简﹣x2﹣(3x﹣5y)+[4x2﹣(3x2﹣x﹣y)],再求值,其中x=,y=.
54.先化简,再求值:,其中x=﹣2,.
55.先化简,再求值:3()﹣(5x2y﹣4xy2),其中x=2,y=﹣1.
56.先化简,再求值,已知a=1,b=﹣,求多项式的值.
57.先化简,再求值:3(x2﹣xy)﹣(4x2﹣3xy﹣1),其中.
58.先化简,再求值:,其中.
59.先化简,再求值:2(x2y﹣xy2﹣1)﹣(2x2y﹣xy2﹣y),其中x=2,y=﹣1.
60.先化简,再求值:(2m2n+2mn2)﹣2(m2n﹣1)﹣3+mn,其中.
61.先化简,再求值.3x﹣5(x﹣2xy2)+8(x﹣3xy2),其中.
62.先化简,再求值:,其中x=﹣2.
63.先化简,再求值:﹣5x2y﹣[3x2y﹣2(xy2﹣x2y)].其中x=2,y=﹣1.
64.先化简,再求值:,其中,y=2008.
65.先化简,再求值:5a2﹣3b2+[﹣(a2﹣2ab﹣b2)﹣(5a2+2ab+3b2)],其中a=1,b=﹣.
66.先化简,再求值:2x2+3x+5+[4x2﹣(5x2﹣x+1)],其中x=3.
67.先简化再求值:
(其中x=﹣2,y=)
68.先化简,再求值.2(a2b+2b3﹣ab2)+3a3﹣(2a2b﹣3ab2+3a3)﹣4b3,其中a=﹣3,b=2.
69.先化简再求值:2(a2b+ab3)﹣3(a2b﹣3)﹣2ab3﹣1,其中a=2,b=﹣2.
70.已知a,b满足等式,求代数式的值.
71.先化简,再求值.4xy﹣[2(x2+xy﹣2y2)﹣3(x2﹣2xy+y2)],其中x=﹣,y=
72.先化简,再求值:2x2+(﹣x2+3xy+2y2)﹣(x2﹣xy+2y2),其中
x=,y=3.
73.先化简,再求值:(2x2﹣5xy)﹣3(x2﹣y2)+x2﹣3y2,其中x=﹣3,y=.
74.先化简,再求值:5a2b+3b2﹣2(3a2b+ab2)+(4a2b﹣3b2),其中a=﹣2,b=1.
75.先化简,再求值:5a﹣[a2+(5a2﹣3a)﹣6(a2﹣2a)],其中a=﹣.
76.先化简再求值:3x2y﹣[2xy2﹣4(xy﹣x2y)+xy]+3xy2,其中x=3,y=﹣1.
77.先化简,再求值:2(a2b+ab2)﹣3(a2b﹣3)﹣2ab2﹣1.其中a=﹣2,b=2.
78.先化简,再求值:,其中x=3,y=.
79.化简后再求值:x﹣2(3y2﹣2x)﹣4(2x﹣y2),其中|x﹣2|+(y+1)2=0.
80.先化简,再求值,5x2﹣(3y2+5x2﹣2xy)+(﹣7xy+4y2),其中:x=﹣1,y=﹣.
81.先化简,再求值:,其中x,y满足(x﹣2)2+|y+3|=0.
82.先化简,再求值:2(x2﹣3xy﹣y2)﹣(2x2﹣7xy﹣2y2),其中x=4,y=﹣1时.
83.求代数式的值:2(3xy+4x2)﹣3(xy+4x2),其中x=﹣3,.
84.先化简,再求值:5(a2b﹣ab2)﹣(ab2+3a2b),其中
85.
先化简,再求值:5(3a2b﹣ab2)﹣(ab2+3a2b)﹣4(3a2b﹣ab2),其中a=﹣2,b=.
86.先化简,再求值:(a2b﹣2ab2﹣b3)÷b+(b﹣a)(b+a),其中a=﹣,b=2012.
87.先化简,再求值:,其中.
88.先化简,再求值:4m3﹣(3m2+5m﹣2)+2(3m+m2﹣2m3)﹣1,其中m=2011.
89.先化简,再求值
2(3x2﹣x+4)﹣3(2x2﹣2x+3),其中.
90.先化简,再求值.2(2xy2﹣y2)﹣(4xy2+y2﹣x2y)﹣y2,其中x=,y=﹣.
整式化简求值90题参考答案:
1.原式=6a2﹣2ab﹣6a2+3ab=ab,当a=﹣2,b=3时,原式=ab=﹣2×3=﹣6.
2.原式=6a2b+3a2b﹣5ab2﹣10a2b+6ab2=﹣a2b+ab2把a=﹣2,b=代入上式得:
原式=﹣(﹣2)2×+(﹣2)×2=﹣2﹣=﹣2.
3.原式=3x2y2﹣5xy2+4xy2﹣3﹣2x2y2
=x2y2﹣xy2﹣3
∴当x=﹣3,y=2时,原式=45
4.原式=5ab2+3a2b﹣3a2b+2ab2(4分)
=7ab2.(6分)
当a=2,b=﹣1时,原式=7×2×(﹣1)2(7分)
=14.
5.原式=2x2﹣y2+2y2﹣x2﹣3x2﹣6y2=﹣2x2﹣5y2.
当x=3,y=﹣2时,原式=﹣18﹣20=﹣38.
6.﹣x2﹣(3x﹣5y)+[4x2﹣(3x2﹣x﹣y)]
=﹣x2﹣3x+5+[4x2﹣3x2+x+y]
=﹣2x+6y,当时,原式=﹣3
7.原式=5x2﹣(x2+5x2﹣2x﹣2x2+6x)
=x2﹣4x
当x=时,上式=
8.原式=6a2﹣6ab﹣12b2﹣6a2+12b2=﹣6ab,当a=﹣,b=﹣8时,原式=﹣6×(﹣)×(﹣8)=﹣24.
9.=﹣a2﹣9a+7
当a=﹣2时,原式=﹣(﹣2)2﹣9×(﹣2)+7
=﹣4+18+7
=21.
10.∵|x﹣y+1|+(x﹣5)2=0,则x﹣y+1=0,x﹣5=0,解得x=5,y=6.
(﹣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,当a=﹣1,b=2时,原式=(﹣1)2×2+(﹣1)×22,=﹣2;
(2)原式=2x3﹣xyz﹣2x3+2y3﹣2xyz﹣xyz﹣2y3,=﹣4xyz,当x=1,y=2,z=﹣3时,原式=﹣4×1×2×(﹣3)=24
12.原式=x2y﹣2xy+x2y+xy=2x2y﹣xy,当x=﹣1,y=﹣2时,原式=2×(﹣1)2×(﹣2)﹣(﹣1)×(﹣2)=﹣6.
13.∵|x﹣2|+|y+1|=0,∴x﹣2=0,y+1=0,解得x=2,y=﹣1,原式=5xy2﹣2x2y+3xy2﹣4xy2+2x2y,=4xy2,=4×2×1,=8
14.原式=﹣9y+6x2+3y﹣3x2=3x2﹣6y,由x=﹣2,y=﹣得:原式=12+2=14
15.∵|x﹣2a|+(y﹣3)2=0
∴x=2a,y=3
∵B﹣2A=4x2﹣6xy+2y2﹣3x﹣y﹣2(2x2﹣3xy+y2+2x+2y)
=4x2﹣6xy+2y2﹣3x﹣y﹣4x2+6xy﹣2y2﹣4x﹣4y
=﹣7x﹣5y
又B﹣2A=a
∴﹣7×2a﹣5×3=a
∴a=﹣1
16.(1)4M﹣3N=4(﹣xy2+3x2y﹣1)﹣3(4x2y+2xy2﹣x)
=﹣4xy2+12x2y﹣4﹣12x2y﹣6xy2+3x
=﹣10xy2+3x﹣4;
(2)当x=﹣2,y=1时,4M﹣3N=﹣10×(﹣2)×1+3×(﹣2)﹣4
=20﹣6﹣4
=10.
17.(1)原式=(5x2﹣3x)﹣2(2x﹣3)+7x2=12x2﹣7x+6,当x=﹣2时,原式=12×(﹣2)2﹣7×(﹣2)+6=68;
(2)原式=2a﹣[4a﹣7b﹣2+6a+4b],=2a﹣[10a﹣3b﹣2],=﹣8a+3b+2,当a=,b=时,原式=6
18.原式=5xy+15x2﹣10y﹣3xy﹣15x2+6y=2xy﹣4y,当x=,y=﹣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
当x=﹣2,y=时,原式=﹣3×(﹣2)+()2=6+
=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
当a=1时
原式=6×1﹣3
=6﹣3
=3
21.化简代数式得,原式=1+a+b;
当a=3时,b=1,代数式的值为5;
当a=﹣3时,b=﹣5,代数式的值为﹣7.
22.a2﹣(2a2+2ab﹣b2)+(a2﹣ab﹣b2)
=a2﹣2a2﹣2ab+b2+a2﹣ab﹣b2
=﹣a2﹣3ab.
当a=3,b=﹣2时,原式=﹣×32﹣3×3×(﹣2)
=﹣3+18
=15
23.原式=2a2﹣ab+b2其中a=﹣1,b=2.所以2a2﹣ab+b2=8
24.原式=3a2b﹣(2ab2﹣2ab+3a2b+ab)+3ab2=ab2+ab;
将a=3,b=﹣代入得,原式=ab2+ab=﹣
25.∵3xa﹣2y2z3和﹣4x3yb﹣1z3是同类项
∴a﹣2=3,b﹣1=2
∴a=5,b=3.
3a2b﹣[2ab2﹣2(a2b+2ab2)]
=3a2b﹣[2ab2﹣2a2b﹣4ab2]
=3a2b﹣2ab2+2a2b+4ab2
=5a2b+2ab2当a=5,b=3时,原式=5×52×3+2×5×32=465.
26.﹣8xy2+3xy﹣2(xy2﹣xy)
=﹣8xy2+3xy﹣2xy2+2xy
=﹣10xy2+5xy.
当x=,y=﹣2时,原式=﹣10xy2+5xy
=﹣10××(﹣2)2+5××(﹣2)
=﹣8﹣2
=﹣10
27.(1)2A﹣B=2(3x2+3y2﹣5xy)﹣(2xy﹣3y2+4x2)
=6x2+6y2﹣10xy﹣2xy+3y2﹣4x2=2x2+9y2﹣12xy;
(2)当时,2A﹣B=2x2+9y2﹣12xy=31
28.原式=2a2b+2ab2﹣2ab2+1﹣a2b﹣2
=a2b﹣1,当a=﹣2,b=时,∴原式=a2b﹣1=(﹣2)2×﹣1=2﹣1=1.
29.2(a2﹣2ab)﹣3(a2+2ab)
=2a2﹣4ab﹣3a2﹣6ab
=﹣a2﹣10ab
当a=﹣1,b=2时,原式=﹣(﹣1)2﹣10×(﹣1)×2
=﹣1+20
=19.
30.(1)A=4(2﹣x2)﹣2x,B=2x2﹣x+3.
A﹣2B=4(2﹣x2)﹣2x﹣2(2x2﹣x+3)
=﹣8x2+2
当x=时,A﹣2B=﹣8×()2+2=;
(2)A=4(2﹣x2)﹣2x,B=2x2﹣x+3,即:2B=4x2﹣2x+6,由于A与2B互为相反数,即:A+2B=0,4(2﹣x2)﹣2x+4x2﹣2x+6=0
4x=14,解得:x=
所以,x的值为:.
31.原式=5abc﹣2a2b﹣4ab2+a2b+3abc=8abc﹣a2b﹣4ab2;
a=﹣2,b=﹣1,c=3时,原式=8×2×1×3﹣4×(﹣1)﹣4×(﹣2)×1=60.
32.2(x2y+xy2)﹣2(x2y﹣x)﹣2xy2﹣2y
=2x2y+2
xy2﹣2x2y+2x﹣2xy2﹣2y
=2x﹣2y;
把x=﹣2,y=2代入上式,原式=2×(﹣2)﹣2×2=﹣8
33.原式=﹣2ab+6a2﹣(a2﹣5ab+5a2+6ab)
=﹣2ab+6a2﹣a2+5ab﹣5a2﹣6ab
=﹣3ab;
当a=2,b=﹣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
当a=2,b=﹣1时,则原式=15×2﹣1=29.
35.原式=5a2b+4b3﹣2ab2+3a3﹣2a3+5ab2﹣3b3﹣2a2b
=a3+3a2b+3ab2+b3,当a=﹣2,b=3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
把a=1,b=﹣2代入上式,得
上式=2×1﹣(﹣2)2
=2﹣4
=﹣2.
37.原式=a2﹣3ab﹣2b2﹣a2+2b2(3分)
=﹣3ab,当,b=﹣8时,原式=﹣3×()×(﹣8)(7分)
=﹣12.
38.原式=2x2﹣0.5+3x﹣4x+4x2﹣2+x+2.5
=6x2;
当x=时,原式=6×=.
39.原式=3x3﹣6y2﹣3xy﹣3x3+6y2﹣2xy
=﹣5xy,当x=3,y=1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,当x=,y=﹣5时,原式=×(﹣5)+×25=.
41.原式=8mn﹣[4m2n﹣6mn2﹣mn]﹣29mn2=8mn﹣4m2n+6mn2+mn﹣29mn2=9mn﹣4m2n﹣23mn2当m=﹣1,n=时
原式=9×(﹣1)×﹣4×12×﹣23×(﹣1)×
=﹣﹣2+
=﹣.
42.原式=4ab﹣3b2﹣2b2
=4ab﹣5b2,当a=1,b=﹣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,当x=﹣2时,原式=﹣(﹣2)2﹣(﹣2)+3=1
44.(2x2﹣x﹣1)﹣(x2﹣x﹣)+(3x2﹣3)
=2x2﹣x﹣1﹣x2+x++3x2﹣3
=4x2﹣4,当x=,原式=1﹣4=﹣3.
45.原式=3x2﹣3xy﹣3x2+5xy
=2xy,当x=﹣2,y=﹣3时,原式=2×(﹣2)×(﹣3)=12.
46.原式=3xy﹣x2y﹣2xy+x2y+2…(1分)
=xy+2…(2分)
∵xy+1=0,∴xy=﹣1…(3分)
∴原式=﹣1+2=1…(4
47.原式=12x2y﹣4xy2﹣2xy2﹣6x2y
=6x2y﹣6xy2
当x=,y=﹣1时,原式=6x2y﹣6xy2=6xy(x﹣y)=6×(﹣)×(+1)
=
=﹣4.
48.原式=x2﹣y﹣x2﹣y=﹣x2﹣y,当x=﹣3,y=﹣时
原式=﹣×(﹣3)2﹣(﹣)=﹣3+=﹣.
49.原式=4xy﹣2x2﹣5xy+y2+2x2+6xy)
=5xy+y2.
当x=﹣2,y=1时,原式=5×(﹣2)+1=﹣9.
50.(8xy﹣3x2)﹣5xy﹣3(xy﹣2x2+3)
=8xy﹣3x2﹣5xy﹣3xy+6x2﹣9
=3x2﹣9,当时,原式=
51.原式=x2﹣[7x﹣2x+﹣2x2]+
=x2﹣7x+2x﹣+2x2+
=3x2﹣5x
当x=﹣时,原式=3×(﹣)2+5×=+=.
52.3a2﹣7a+[3a﹣2(a2﹣2a﹣1)]
=3a2﹣7a+3a﹣2a2+4a+2
=a2+2,当d=﹣2时,原式=4+4=8.
53.﹣x2﹣(3x﹣5y)+[4x2﹣(3x2﹣x﹣y)]=﹣x2﹣3x+5y+[4x2﹣3x2+x+y]=﹣x2﹣3x+5y+4x2﹣3x2+x+y=﹣2x+6y.
当x=,y=时,原式=﹣2×+6×=1
54.原式=x﹣x+y2﹣x+y2=﹣2x+y2,当x=2,y=时,原式=﹣2×2+()2=﹣4+=﹣.
55.原式=x2y﹣3xy2﹣5x2y+4xy2
=﹣x2y+xy2,当x=2,y=﹣1时,原式=﹣×22×(﹣1)+2×(﹣1)2
=16
56.=a3﹣2b3+2ab2﹣a2b﹣2ab2+2b3
=a3﹣a2b,把a=1,b=﹣代入得:
原式=13﹣12×
=1+
=.
57.原式=3x2﹣3xy﹣4x2+3xy+1
=﹣x2+1,当x=2,y=﹣3时,原式=﹣22+1=﹣3.
58.原式=9x+6x2﹣3x+2x2﹣6x+6
=8x2+6,当x=﹣时,原式=8×(﹣)2+6=2+6=8.
59.原式=2x2y﹣2xy2﹣2﹣2x2y+xy2+y=﹣xy2+y﹣2,当x=2,y=﹣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,当m=﹣2,n=时,原式=2×(﹣2)×()2+(﹣2)×﹣1=﹣3
61.3x﹣5(x﹣2xy2)+8(x﹣3xy2)=3x﹣5x+10xy2+8x﹣24xy2=6x﹣14xy2,当x=4,y=﹣时,原式=6×4﹣14×4×(﹣)2=24﹣126=﹣102.
62.(2x2﹣x+1)﹣4(x﹣x2+)=2x2﹣x+1﹣4x+4x2﹣2=6x2﹣x﹣1,当x=﹣2时,原式=6×(﹣2)2﹣×(﹣2)﹣1=24+9﹣1=32
63.原式=﹣5x2y﹣3x2y+2xy2﹣2x2y=2xy2,当x=2,y=﹣1时,原式=2×2×(﹣1)2=4.
故答案为4
64.原式=﹣x2+x﹣2y+x+2y=﹣x2+x,当x=,y=2008时,原式=﹣()2+×=﹣+=.
65.原式=5a2﹣3b2﹣a2+2ab+b2﹣5a2﹣2ab﹣3b2
=﹣a2﹣5b2,当a=1,b=﹣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,∵x=3,∴x2+4x+4=9+12+4
=25.
67.原式=x2﹣xy+y2﹣x2+xy﹣y2=﹣x2﹣xy,当x=﹣2,y=时,原式=﹣2+=﹣1.
68.原式=2a2b+4b3﹣2ab2+3a3﹣2a2b+3ab2﹣3a3﹣4b3=ab2,当a=﹣3,b=2时,原式=﹣3×22=﹣12.
69.原式=2a2b,2ab3﹣3a2b+9﹣2ab3﹣1
=2a2b﹣3a2b+2ab3﹣2ab3+9﹣1
=﹣a2b+8
∵a=2,b=﹣2,∴﹣a2b+8=8+8=16
70.∵,∴a+=0,3b+2=0,∴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,∴当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,当x=,y=3时,原式=4××3=6
73.原式=2x2﹣5xy﹣3x2+3y2+x2﹣3y2=(2﹣3+1)x2+(3﹣3)y2﹣5xy
=﹣5xy,当x=﹣3,y=时,原式=(﹣5)×(﹣3)×=5
74.原式=5a2b+3b2﹣6a2b﹣2ab2+4a2b﹣3b2=3a2b﹣2ab2,当a=﹣2,b=1时,原式=12+4=16.
75.原式=5a﹣a2﹣5a2+3a+6a2﹣12a=8a﹣12,当a=﹣时,原式=﹣2﹣12=﹣14.
76.原式=3x2y﹣[2xy2﹣2xy+3x2y+xy]+3xy2=3x2y﹣2xy2+xy﹣3x2y+3xy2=xy2+xy,把x=3,y=﹣1代入得:原式=xy2+xy=0
77.2(a2b+ab2)﹣3(a2b﹣3)﹣2ab2﹣1,=2a2b+2ab2﹣3a2b+9﹣2ab2﹣1,=﹣a2b+8,当a=﹣2,b=2时,原式=﹣(﹣2)2×2+8=0.
78.原式=﹣3x+5y2﹣+
=﹣4x+y2,当x=3,y=时,原式=(﹣4)×3+×()2=0.
79.∵|x﹣2|+(y+1)2=0,∴x=2,y=﹣1,x﹣2(3y2﹣2x)﹣4(2x﹣y2)=x﹣6y2+4x﹣8x+4y2=﹣3x﹣2y2,当x=2,y=﹣1时,原式=﹣6﹣2=﹣8.
80.原式=5x2﹣3y2﹣5x2+2xy﹣7xy+4y2=﹣5xy+y2,当x=﹣1,y=﹣时,原式=﹣5×(﹣1)×(﹣)+(﹣)2=﹣+=﹣.
81.原式==﹣3x+y2,由(x﹣2)2+|y+3|=0,知x﹣2=0,y+3=0,解得x=2,y=﹣3,代入化简结果得,原式=﹣3×2+(﹣3)2=3
82.原式=x2﹣6xy﹣2y2﹣2x2+7xy+2y2=﹣x2+xy,当x=4,y=﹣1时,原式=﹣42+4×(﹣1)=﹣20
83.∵原式=5a2b﹣5ab2﹣ab2﹣3a2b
=2a2b﹣6ab2,∴当时,原式==.
84.∵原式=5a2b﹣5ab2﹣ab2﹣3a2b
=2a2b﹣6ab2,∴当时,原式==.
85.原式=15a2b﹣5ab2﹣ab2﹣3a2b﹣12a2b+4ab2=﹣2ab2,当a=﹣2,b=时,原式=﹣2×(﹣2)×=1
86.原式=a2﹣2ab﹣b2+b2﹣a2=﹣2ab,当a=﹣,b=2012时,原式=﹣2×(﹣)×2012=2012.
87.原式=2x﹣y﹣6x+y=﹣4x,当x=﹣,y=2010时,原式=﹣4×(﹣)=1.
88.原式=6x2﹣2x+8﹣6x2+6x﹣9=4x﹣1,当时,原式==﹣7.
89.原式=6x2﹣2x+8﹣6x2+6x﹣9=4x﹣1,当时,原式==﹣7.
90.原式=4xy2﹣y2﹣4xy2﹣y2+x2y﹣y2=﹣3y2+x2y.
当x=,y=﹣时,原式=﹣3×(﹣)2+()2×(﹣)
=
=.