x^2-y^2+4y-4x=

问题描述:

x^2-y^2+4y-4x=
x-y-kx+ky=

x^2-y^2+4y-4x
=(x+y)(x-y)-4(x-y)
=(x-y)(x+y-4)
x-y-kx+ky
=(x-y)-k(x-y)
=(x-y)(1-k)