一、因式分解
1.x(x+y)(x-y)-x(x+y)^2
=x[x+y][x-y-x-y]
=-2xy[x+y]
2.(a+b)(a-b)-(b+a)
=[a+b][a-b-1]
3.(m+n)^2-n^2
=[m+n+n][m+n-n]
=m[m+2n]
4.(x^2+y^2)^2-x^2y^2
=[x^2+y^2+xy][x^2+y^2-xy]
5.(a+b+c)^2-(a+b-c)^2
=[a+b+c+a+b-c][a+b+c-a-b+c]
=2c[2a+2b]
=4c[a+b]
6.4(x-2)^2-9x^2
=[2(x-2)+3x][2(x-2)-3x]
=[5x-4][-x-4]
=-[5x-4][x+4]