Đáp án `+` Giải thích các bước giải:

`1) 2x^2 - 12x + 18 + 2xy - 6y`

`= ( 2x^2 - 12x + 18 ) + (2xy - 6y)`

`= 2(x^2 - 6x + 9) + 2y(x - 3)`

`= 2(x-3)^2 + 2y(x-3)`

`= 2(x-3)(x-3+y)`

`2) x^2 + 4x - 4y^2 + 8y`

`= (x^2 - 4y^2 ) + (4x + 8y)`

`= (x-2y)(x+2y) + 4(x+2y)`

`= (x-2y + 4)(x + 2y)`

`3) x^2 + 2x - 4y^2 + 4y`

`= (x^2 - 4y^2) + (2x + 4y)`

`= (x-2y)(x+2y) + 2(x+2y)`

`= (x-2y+2)(x+2y)`

`4) y^2 - x^2 - 12y + 36`

`= (y^2 - 12y + 36 ) - x^2`

`= (y-6)^2 - x^2`

`= (y-6-x)(y-6+x)`

`5) x^2 + 10x - 16y^2 + 25`

`= (x^2 + 10x + 25) - 16y^2`

`= (x+5)^2 - 16y^2`

`= (x+5-4y)(x+5+4y)`