ax-bx-x+ay-by-y=x(a-b)-x+y(a-b)-y=(a-b)(x+y)-x-y=-(a-b)(x+y)^2
2a^2-a+2ab-b-2ac+c=a(2a-1)+b(2a-1)-c(2a-1)=(2a-1)(a+b-c)
a^5-a^4b+a^3b^2-a^2b^3+ab^4-b^5=a^4(a-b)+a^2b^2(a-b)+b^4(a-b)=
=(a-b)(a^4+a^2b^2+b^4)
px^2+qx+q^2y+pqxy+p^2qx+pq^2=x(px+q)+q^2(p+y)+pqx(y+p)=
=(y+p)(q^2+pqx)+x(px+q)=(y+p)(q+x)(q+px)