Cách làm cho bạn:
a) x2 – xy + x – y = (x2 – xy) + (x – y)
= x(x – y) + (x – y)
= (x – y)(x + 1)
b) xz + yz – 5(x + y) = z(x + y) – 5(x + y)
= (x + y)(z – 5)
c) 3x2 – 3xy – 5x + 5y = (3x2 – 3xy) – (5x – 5y)
= 3x(x – y) – 5(x – y)
= (x – y)(3x – 5).
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