1.因式分解x^2 y - y^2 z + z^2 x-x^2 z +y^2 x + z^2 y -2xyz
=z^2(x+y)+xy*(x+y)-z(x^2+2xy+y^2)
=z^2(x+y)+xy(x+y)-z(x+y)^2
=(x+y)*(z^2+xy-zx-zy)
=(x+y)[z(z-x)-y(z-x)]
=(x+y)(Z-x)(z-y)
2.x^2 - (m^2 + n^2 ) x +mn (m^2 -n^2 )
=x^2-(m^2+n^2)+[n(m+n)m(m-n)]
=[x-n(m+n)][x-m(m-n)]
=(x-mn-n^2)(x-m^2+mn)
3.(c-2 )^2 - 4 (b-c)(a-b)
=题目对吗?