Đáp án+Giải thích các bước giải:

`a;  ( x + 2 )^2 -x( x + 3 ) = 2`

`<=> x^2 + 4x + 4 - x^2 - 3x = 2`

`<=> x = -2`

` Vậy  x = -2`

`b; (x+ 2 )( x - 2 ) - ( x + 1 )^2 = 7`

`<=> x^2 - 4 - x^2 - 2x - 1 = 7`

`<=> 2x = -12`

`<=> x= -6`

` Vậy  x = -6`

`c; 6x^2 - ( 2x + 1 )( 3x - 2 ) = 1`

`<=> 6x^2 - ( 6x^2 - x - 2 ) = 1`

`<=> 6x^2 - 6x^2 + x + 2 = 1`

`<=> x = -1`

` Vậy  x = -1`

`d; ( x + 2 )( x + 3 ) - ( x - 2 )( x + 1 ) = 2`

`<=> x^2 + 5x + 6 - ( x^2 - x - 2 ) = 2`

`<=> x^2 + 5x + 6 - x^2 + x + 2 = 2`

`<=> 6x = -6`

`<=> x = -1`

` Vậy  x = -1`

`e; 6( x - 1)( x + 1 ) - ( 2x - 1 )( 3x + 2 ) + 3 = 0`

`<=> 6( x^2 - 1 ) - ( 6x^2 + x - 2 ) + 3 = 0`

`<=> 6x^2 - 6 - 6x^2 - x + 2 + 3 = 0`

`<=> x = -1`

` Vậy  x = -1`

`f; x( 3x + 1 ) + ( x - 1 )^2 - ( 2x + 1 )( 2x - 1 ) = 0`

`<=> 3x^2 + x + x^2 - 2x + 1 - 4x^2 + 1 = 0`

`<=> x = 2`

` Vậy  x = 2`

`g;  ( x + 1 )^3 + ( 2 - x )^3 - 9( x - 3 )( x + 3 ) = 0`

`<=> x^3 + 3x^2 + 3x + 1 + 8 - 12x + 6x^2 - x^3 - 9x^2 + 81 = 0`

`<=> 9x = 90`

`<=> x = 10`

` Vậy  x = 10`

`i;  ( x - 1 )^3 - ( x + 3 )( x^2 - 3x + 9 ) - 3x^2 = 25`

`<=> x^3 - 3x^2 + 3x - 1 - x^3 - 27 - 3x^2 = 25`

`<=> -6x^2 + 3x - 53 = 0`

`<=> x^2 - x/2 + 53/6 = 0`

`<=> x^2 - 2 . 1/4x + 1/16 = -421/48`

`<=> ( x - 1/4 )^2 = -421/48` ( vô lí )

` Vậy  x in ∅`