x^4+x^3-x^2-x
=(x^4+x^3)-(x^2+x)
=x^2(x^2+x)-(x^2+x)
=(x^2+x)(x^2-1)
=x(x+1)(x+1)(x-1)
=x(x+1)^2(x-1)
1-m^2-2mn+2n
=1-m^2-(2mn-2n)
=(1-m)(1+m)-2n(m-1)
=(1-m)(1+m)+2n(1-m)
(1-m)(1+m+2n)