初一10道化简求值题

1、已知A,B是方程x^2+2x-5=0的两个实数根,
求(A^2+2AB+2A)(B^2+2AB+2B)的值.
由A,B是方程x^2+2x-5=0的两个实数根得：
AB=-5，A+B=-2
A^2+2AB+2A)(B^2+2AB+2B)
=AB（A+2B+2）（B+2A+2）
=-5（-2+B+2）（-2+A+2）
=-5AB
=25

2、1/2(x+y+z)方+1/2(x-y-z)(x-y+z)-z(x+y),其中x-y=6,xy=21.要详细步骤
化简得：
1/2(x+y+z)方+1/2(x-y-z)(x-y+z)-z(x+y)=
1/2[(x+y)方+2z(x+y)+z方]+1/2[(x-y)方-z方]-z(x+y)=
1/2(x+y)方+1/2(x-y)方=x方＋y方
由x-y=6,xy=21得，x方＋y方＝（x-y）方＋2xy＝78

3、a^2-ab+2b^2=3 求2ab-2a^2-4b^2-7的值
2ab-2a^2-4b^2-7
=2(ab-a^2-2b^2)-7
=-2(a^2-ab+2b^2)-7
=(-2)*3-7
=-6-7=-13

4、若A=2x^2+3xy-2x-3,B=-x^2+xy+2,且3A+6B的值与x无关，求y的值
解：
3A+6B=6x^2+9xy-6x-9-6x^2+6xy+12
=15xy-6x+3
=x(15y-6)+3

5、9x+6x^2 -3(x-2/3x^2).其中x=-2
9x+6x�0�5 -3(x-2/3x�0�5)
=9x+6x�0�5-3x+2x�0�5
=8x�0�5+6x
=8×(-2)�0�5+6×(-2)
=32-12
=20

6、1/4(-4x^2+2x-8)-(1/2x-1),其中x=1/2
1/4(-4x�0�5+2x-8)-(1/2x-1)
=-x�0�5+1/2x-2-1/2x+1
=-x�0�5-1
=-(1/2)�0�5-1
=-1/4-1
=-5/4

7、3x'y-[2x'y-(2xyz-x'z)-4x'z]-xyz,其中x=-2,y=-3,z=1,
:3x'y-[2x'y-(2xyz-x'z)-4x'z]-xyz
=3x'y-2x'y+2xyz-x'z+4x'z-xyz
=x'y-xyz+3x'z
=4*(-3)-2*3*1+3*4*1
=-12-6+12
=-6

8、(5a^2-3b^2)+(a^2+b^2)-(5a^2+3b^2),其中a=-1,b=1
=5a^2-3b^2+a^2+b^2-5a^2-3b^2
=a^2-5b^2
=(-1)^2-5*1^2
=1-5
=-4

9、2(a^2b+ab^2)-2(a^2 b-1)-2ab^2 -2其中a=-2,b=2
=2a^2b+2ab^2-2a^2b+2-2ab^2-2
=0

10、(X-2分之1Y-1)(X-2分之1Y+1)-(X-2分之1Y-1)的平方
其中X=1.7,Y=3.9(先化简再求值)
[(X-2分之1Y)-1][(X+2分之1Y)+1]-(X-2分之1Y-1)平方
=(X+2分之1Y)平方-1-(X-2分之1Y)平方+2(X-2分之1Y)-1
=(X+2分之1Y)平方-(X-2分之1Y)平方+2(X-2分之1Y)-2
=2XY+2X-Y-2
=3.9*2.4+1.4
=10.76

希望对你有帮助。3ab-4ab+8ab-7ab+ab=______．

7x-(5x-5y)-y=______．

23a3bc2-15ab2c+8abc-24a3bc2-8abc=______．

-7x2+6x+13x2-4x-5x2=______．

2y+(-2y+5)-(3y+2)＝______．

(2x2-3xy+4y2)+(x2+2xy-3y2)=______．

2a-(3a-2b+2)+(3a-4b-1)=______．

-6x2-7x2+15x2-2x2＝______．

2x-(x+3y)-(-x-y)-(x-y)＝______．

2x+2y-[3x-2(x-y)]=______．

5-(1-x)-1-(x-1)=______．

(4xy2-2x2y)-( )=x3-2x2y+4xy2+y3．

已知A=x3-2x2+x-4，B=2x3-5x+3，计算A+B=______．

已知A=x3-2x2+x-4，B=2x3-5x+3，计算A-B=______．

若a=-0.2，b=0.5，代数式-(|a2b|-|ab2|)的值为______．

1．若a=-0.2，b=0.5，代数式-(|a2b|-|ab2|)的值为______．

2．一个多项式减去3m4-m3-2m+5得-2m4-3m3-2m2-1，那么这个多项式等于______．

3．-(2x2-y2)-[2y2-(x2+2xy)]=______．

4．若-3a3b2与5ax-1by+2是同类项，则x=______，y=______．

5．(-y+6+3y4-y3)-(2y2-3y3+y4-7)＝______．

6．化简代数式4x2-[7x2-5x-3(1-2x+x2)]的结果是______．

7．2a-b2+c-d3=2a+( )-d3=2a-d3-( )=c-( )．

8．3a-(2a-3b)+3(a-2b)-b=______．

9．化简代数式x-[y-2x-(x+y)]等于______．

10．[5a2+( )a-7]+[( )a2-4a+( )]=a2+2a+1．

当a等于5，b等于5时，3ab-4ab+8ab-7ab+ab的值是多少 下面的都是这种形式

7x-(5x-5y)-y=______．

23a3bc2-15ab2c+8abc-24a3bc2-8abc=______．

-7x2+6x+13x2-4x-5x2=______．

2y+(-2y+5)-(3y+2)＝______．

(2x2-3xy+4y2)+(x2+2xy-3y2)=______．

2a-(3a-2b+2)+(3a-4b-1)=______．

-6x2-7x2+15x2-2x2＝______．

2x-(x+3y)-(-x-y)-(x-y)＝______．

2x+2y-[3x-2(x-y)]=______．

5-(1-x)-1-(x-1)=______．

(4xy2-2x2y)-( )=x3-2x2y+4xy2+y3．

已知A=x3-2x2+x-4，B=2x3-5x+3，计算A+B=______．

已知A=x3-2x2+x-4，B=2x3-5x+3，计算A-B=______．

若a=-0.2，b=0.5，代数式-(|a2b|-|ab2|)的值为______．