b) x^2 + xy – 3x – 3y;
b) x2 + xy – 3x – 3y;
b) Cách 1:
x2 + xy – 3x – 3y
= (x2 + xy) – (3x + 3y)
= x(x + y) – 3(x + y)
= (x + y)(x – 3).
Cách 2:
x2 + xy – 3x – 3y
= (x2 ‒ 3x) + (xy ‒ 3y)
= x(x ‒ 3) + y(x ‒ 3)
= (x ‒ 3)(x + y).