x2-y2-z2-2yz+1-2x
=x^2-2x+1-(y^2+2yz+z^2)
=(x-1)^2-(y+z)^2
=(x-1+y+z)(x-1-y-z)
=(x+y+z-1)(x-y-z-1)
x2-6xy-10x+30 y+25
=x^2-10x+25-6xy+30y
=(x-5)^2-6y(x-5)
=(x-5)(x-5-6y)
=(x-5)(x-6y-5)