化简
1．(4x2-8x+5)-(x3+3x2-6x+2)．
2．(0.3x3-x2y+xy2-y3)-(-0.5x3-x2y+0.3xy2)．
3．-{2a2b-[3abc-(4ab2-a2b)]｝．
4．(5a2b+3a2b2-ab2)-(-2ab2+3a2b2+a2b)．
5．(x2-2y2-z2)-(-y2+3x2-z2)+(5x2-y2+2z2)．
6．(3a6-a4+2a5-4a3-1)-(2-a+a3-a5-a4)．
7．(4a-2b-c)-5a-[8b-2c-(a+b)]．
8．(2m-3n)-(3m-2n)+(5n+m)．
9．(3a2-4ab-5b2)-(2b2-5a2+2ab)-(-6ab)．
10．xy-(2xy-3z)+(3xy-4z)．
11．(-3x3+2x2-5x+1)-(5-6x-x2+x3)．
12．3x-(2x-4y-6x)+3(-2z+2y)．
13.4x-2(x-3)-3[x-3(4-2x)+8]．
14．(-x2+4+3x4-x3)-(x2+2x-x4-5)．
15．若A=5a2-2ab+3b2,B=-2b2+3ab-a2,计算A+B．
16．已知A=3a2-5a-12,B=2a2+3a-4,求2(A-B)．
17．2m-{-3n+[-4m-(3m-n)]｝．
18．5m2n+(-2m2n)+2mn2-(+m2n)．
19．4(x-y+z)-2(x+y-z)-3(-x-y-z)．
20．2(x2-2xy+y2-3)+(-x2+y2)-(x2+2xy+y2)．
将下列各式先化简,再求值
1．已知a+b=2,a-b=-1,求3(a+b)2(a-b)2-5(a+b)2×(a-b)2的值．
2．已知A=a2+2b2-3c2,B=-b2-2c2+3a2,C=c2+2a2-3b2,求(A-B)+C．
3．求(3x2y-2xy2)-(xy2-2x2y),其中x=-1,y=2．
4．已知|x+1|+(y-2)2=0,求代数式5(2x-y)-3(x-4y)的值．
5．当P=a2+2ab+b2,Q=a2-2ab-b2时,求P-[Q-2P-(P-Q)]．
6．求2x2-｛-3x+5+[4x2-(3x2-x-1)]｝的值,其中x=-3．
7．当x=-2,y=-1,z=3时,求5xyz-｛2x2y-[3xyz-(4xy2-x2y)]｝的值．
8．已知A=x3-5x2,B=x2-6x+3,求A-3(-2B)．
