1. ax + ay - bx - by= (ax + ay) - (bx - by)
=a(x+y)-b(x-y)=(x-y)(a-b)
2. ax + ay - 2x - 2y =(ax + ay)-(2x-2y)
=a(x+y)-2(x-y)=(x-y)(a-2)
3. -2x - 2y + ax + ay=(-2x-2y)+(ax + ay)
=-2(x-y)+a(x+y)=(x-y)(-2-a)
4. x² + xy - 2x - 2y
=(x²+xy)-(2x-2y)
=x(x+y)-2(x-y).
Xin hay nhất ạ