a^2-b^2-a+b = (a-b)(a+b-1),x^3-x^2y-xy^2+y^3 = (x-y)(x^2+xy+y^2),a^3+a^2b-ab^2-b^3 = (a-b)(a^2+ab+b^2+a+b),m^2+2mn+n^2-mb-nb = (m+n)^2-(m+n)b-b = (m+n+m)(m+n)-b(m+n) = (m+n-b)(m+n),xc-yc-x^2+2xy-y^2 = (x-y)(c+x-y).
a^2-b^2-a+b = (a-b)(a+b-1),
x^3-x^2y-xy^2+y^3 = (x-y)(x^2+xy+y^2),
a^3+a^2b-ab^2-b^3 = (a-b)(a^2+ab+b^2+a+b),
m^2+2mn+n^2-mb-nb = (m+n)^2-(m+n)b-b = (m+n+m)(m+n)-b(m+n) = (m+n-b)(m+n),
xc-yc-x^2+2xy-y^2 = (x-y)(c+x-y).