我有几道很难数学题,跪求大家解答.

1) x2y-y2z+z2x-x2z+y2x+z2y-2xyz
=x2(y-z)-yz(y-z)+x(y-z)2
=(y-z)(x2-yz+xy-xz)
=(y-z)(x-z)(x+y)
2) x2-(m2+n2)x+mn(m2-n2)
=x2-(m2+n2)x+(mn+n2)(m2-mn)
=(x-mn-n2)(x-m2+mn)
3) (c-a)2-4(b-c)(a-b)
=c2-2ac+a2+4b2-4(a+c)b+4ac
=(c+a)2-4(a+c)b+4b2
=(c+a-2b)2
打了这么多累死我了

1)x2y-y2z+z2x-x2z+y2x+z2y-2xyz
=2(xy-yz+zx-xz+yx+zy-xyz)
=2(2xy-xyz)
=2xy(2-z)
2) x2-(m2+n2)x+mn(m2-n2)
=x2-(m2+n2)x+(mn+n2)(m2-mn)
=(x-mn-n2)(x-m2+mn)
3) (c-a)2-4(b-c)(a-b)
=c2-2ac+a2+4b2-4(a+c)b+4ac
=(c+a)2-4(a+c)b+4b2
=(c+a-2b)2