Đáp án+Giải thích các bước giải:

`a) xy - 3x = x( y - 3 )`

`b) x^2 + 4xy + 4y^2 - 25`

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

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

`c) x^2 - 10x + 25`

`= ( x - 5 )^2`

`d) ( x - 1 )( x - 2 )( x + 7 )( x + 8 ) + 8`

`= [ ( x - 1 )( x + 7 ) ][ ( x - 2 )( x + 8 ) ] + 8`

`= ( x^2 + 6x - 7 )( x^2 + 6x - 16 ) + 8`

`= ( x^2 + 6x - 7 )^2 - 9( x^2 + 6x - 7 ) + 8`

`= ( x^2 + 6x - 7 )^2 - ( x^2 + 6x - 7 ) - 8( x^2 + 6x - 7 )+ 8`

`= ( x^2 + 6x - 7 )( x^2 + 6x - 8 ) - 8( x^2 + 6x - 8 )`

`= ( x^2 + 6x - 15 )( x^2 + 6x - 8 )`

______________

`a) 3x( x - 1 ) + x - 1 = 0`

`( x - 1 )( 3x + 1 ) = 0`

`x = 1  hoặc  x = -1/3`

`Vậy  x in { 1 ; -1/3 }`

`b) x^2 - 6x = 0`

`x( x - 6 ) = 0`

`x = 0  hoặc  x = 6`

`Vậy  x in { 0 ; 6 }`