六年级数学代数式化简题

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．