Question

急！！！！！几道初一数学题

分解因式：a^3-a，b^2（x-3)+b^2（3-x),16(m-n)^2-9(m+n)^2,4x^2(x-y)+(y-x),4-x^2-4xy-4y^2。计算：(x-y+2)(x+y+2),(3x-2y-1)(3x+2y+1), -4x^3y*[7x^2y-3xy+(2xy)^3]。先化简再求值：x(2x+1)(1-2x)-4x(x-1)(1-x),其中x=-1/2。解二元一次方程组：式子一:y/3-y/2=1,式子二：2x+3y=-2。填空：若m^2-2m+n^2+4n=-5，则m+n=?，已知方程组3x+2y=m+2,2x+3y=m的解适合x+y=8,则m=?.以上就是题目，急呀！！！！要写过程，还要规范，最佳答案另有追加分！

Answer 1

a^3-a
=a(a^2-1)
=a(a-1)(a+1)

b^2（x-3)+b^2（3-x)
=b^2(x-3)-b^2(x-3)
=0

16(m-n)^2-9(m+n)^2
=[4(m-n)-3(m+n)][4m-4n+3m+3n]
=(4m-4n-3m-3n)(7m-n)
=(m-7n)(7m-n)

4x^2(x-y)+(y-x)
=4x^2(x-y)-(x-y)
=(4x^2-1)(x-y)
=(2x-1)(2x+1)(x-y)

4-x^2-4xy-4y^2
=4-(x^2+4xy+4y^2)
=4-(x+2y)^2
=(2-x-2y)(2+x+2y)

计算：(x-y+2)(x+y+2)
=(x+2-y)(x+2+y)
=(x+2)^2-y^2
=x^2+4x+4-y^2

(3x-2y-1)(3x+2y+1),
=[3x-(2y+1)](3x+2y+1)
=(3x)^2-(2y+1)^2
=9x^2-4y^2-4y-1

-4x^3y*[7x^2y-3xy+(2xy)^3]
= -4x^3y*xy(7x-3+8x^2y^2)
= -4x^4y^2(7x-3+8x^2y^2)
= -28x^5y^2+12x^4y^2-32x^6y^4

x(2x+1)(1-2x)-4x(x-1)(1-x)

=x[1-4x^2+4(x-1)^2]
=x(1-4x^2+4x^2-8x+4)
=x(1-8x+4)
=x(5-8x)
=5x-8x^2
=5*(-1/2)-8*1/4
=-2.5-2
=-4.5

y/3-y/2=1,式子二：2x+3y=-2
(这题题目应该抄错了)

m^2-2m+n^2+4n=-5
m^2-2m+1+n^2+4n+4=0
(m-1)^2+(n+2)^2=0
∵(m-1)^2>=0 (n+2)^2>=0
∴m=1 n=-2
m+n=1-2=-1

已知方程组3x+2y=m+2,2x+3y=m的解适合x+y=8,则m=?

将3x+2y=m+2
2x+3y=m

两边相加 得
5x+5y=2m+2
两边÷5
x+y=2/5（m+1）
∴
2/5（m+1）=8
m+1=20
m=19

题目有修改就HI我 我再补充答案！

Answer 2

a^3-a=a(a^2-1)=a(a+1)(a-1)
b^2（x-3)+b^2（3-x)=b^2(x-3+3-x)=0
16(m-n)^2-9(m+n)^2=(4(m-n)+3(m+n))*(4(m-n)-3(m+n))=-(7m-n)^2
4x^2(x-y)+(y-x)
=(4x^2-1)(x-y)=(2x+1)(2x-1))(x-y)
4-x^2-4xy-4y^2=4(1-x^2-xy-y^2)=4(1+x)(1-x)-y(x+y)
(x-y+2)(x+y+2)=(x+2-y)(x+2+y)=(x+2)^2-y^2

(3x-2y-1)(3x+2y+1)= ( 3x+2y+1)(3x-(2y+1)= (3x+2y) ^2--(2y+1)^2

-4x^3y*[7x^2y-3xy+(2xy)^3]=-4x^4y^2(7x-3+8x^2y^2)
x(2x+1)(1-2x)-4x(x-1)(1-x)=x(1-4x^2)+4x(x-1)^2=-4.5
y/3-y/2=1 y=-6 x=10你这道没打错？
m^2-2m+n^2+4n=-5=(m-1)^2+(n+2)^2-5=-5 (m-1)^2+(n+2)^2=0 m=1 n=-2m+n=-1

3x+2y+2x+3y=5X+5y=2m+2=40 m=19
上面那为分解没彻底把

Answer 3

原式=a(a^2-1)=a(a-1)(a+1);
原式=0;
原式=(4m-4n)^2-(3m+3n)^2=[(4m-4n)-(3m+3n)][(4m-4n)+(3m+3n)]=(m-7n)(7m-n)
原式=[（2x)^2-1](x-y)=(2x-1)(2x+1)(x-y)
原式=4-(x^2+4xy+4y^2)=2^2-(x+2y)^2=(2-x-2y)(2+x+2y)
原式=(x+2)^2-y^2=x^2+4xy-y^2+4
原式=(3x)^2-(2y+1)^2=9x^2-4y^2-4y-1
原式=-28x^5y^2+12x^4y^2-32x^6y^4
原式=x(1-4x^2)+4x(x^2-2x+1)=4x^3-4x^3-8x^2+x+4x=-8x^2+5x 当x=-1/2时，原式=1/2-5/2=-2
-1/6y=1 ∴x=-6 ∴-12+3y=-2 ∴y=10/3
原式=(m^2-2m+1)+(n^2+4n+4)=(m-1)^2+(n+2)^2=0
∵(m-1)^2≥0,(n+2)≥0 ∴m-1=0,n+2=0 ∴m=1,n=-2