a) $$ x^3 + 2x^2 + x + 2 = x^2(x+2) + (x+2) = (x^2+1)(x+2) $$.
б) $$ 4x - 4y + xy - y^2 = 4(x-y) + y(x-y) = (4+y)(x-y) $$.
Ответ: a) $$ (x^2+1)(x+2) $$; б) $$ (4+y)(x-y) $$.