Hướng dẫn trả lời:
Bài 2:
d) `a^2.(x - 5) - 3.(x - 5).`
`= (x - 5).(a^2 - 3).`
e) `y.(a - b) - x.(b - a).`
`= y.(a - b) - x.- (a - b).`
`= y.(a - b) + x.(a - b).`
`= (a - b).(y + x).`
`= (a - b).(x + y).`
f) `4.(x - 3)^2 - 2x.(x - 3).`
`= [4.(x - 3) - 2x].(x - 3).`
`= (4x - 12 - 2x).(x - 3).`
`= (2x - 12).(x - 3).`
`= 2.(x - 6).(x - 3).`