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

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!