Đáp án:
`a, 1 - 2y + y^2`
`= 1^2 - 2.1.y + y^2`
`= (1 - y)^2`
`b, (x + 1)^2 - 25`
`= (x + 1)^2 - 5^2`
`= (x + 1 + 5)(x + 1 - 5)`
`= (x + 6)(x - 4)`
`c, 8 - 27x^3`
`= 2^3 - (3x)^3`
`= (2 - 3x)[2^2 + 2.3x + (3x)^2]`
`= (2 - 3x)(4 + 6x + 9x^2)`
`d, 3x^2 + 6x = 3x(x + 2)`
`e, 10x(x - y) - 6y(y - x)`
`= 10x(x - y) + 6y(x - y)`
`= (x - y)(10x + 6y)`
`= (x - y)(5x + 3y).2`
`f, 3x^2 + 5y - 3xy - 5y`
`= (3x^2 - 3xy) + (5y - 5y)`
`= 3x(x - y)`
`g, 5x^2 - 10xy + 5x = 5x(x - 2y + 1)`
`h, x^2 - 4x - 5`
`= x^2 + x - 5x - 5`
`= x(x + 1) - 5(x + 1)`
`= (x + 1)(x - 5)`
`k, 16x - 5x^2 - 3`
`= -5x^2 + 15x + x - 3`
`= (-5x^2 + 15x) + (x - 3)`
`= -5x(x - 3) + (x - 3)`
`= (x - 3)(-5x + 1)`
