Giải giúp mình với ạ

`a)` `2x ( x - 1 ) - 2x^2 = 7`

`<=> 2x ( x - 1 - x ) = 7`

`<=> 2x ( -1 ) = 7`

`<=> 2x = -7`

`<=> x = -7/2`

Vậy `x = -7/2`

`b)` `x ( x - 2 ) + 3 x - 6 = 0`

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

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

`<=>` \(\left[ \begin{array}{l}x+3=0\\x-2=0\end{array} \right.\) 

`<=>` \(\left[ \begin{array}{l}x=-3\\x=2\end{array} \right.\) 

Vậy `x in { -3 ; 2 }`

`c)` `( x^2 - 9 ) + ( x + 5 ) ( x - 3 ) = 0`

`<=> ( x + 3 ) ( x - 3 ) + ( x + 5 ) ( x - 3 ) = 0`

`<=> ( x + 3 + x + 5 ) ( x - 3 ) = 0`

`<=> ( 2x + 8 ) ( x - 3 ) = 0`

`<=>` \(\left[ \begin{array}{l}2x+8=0\\x-3=0\end{array} \right.\) 

`<=>` \(\left[ \begin{array}{l}2x=-8\\x=3\end{array} \right.\) 

`<=>` \(\left[ \begin{array}{l}x=-4\\x=3\end{array} \right.\) 

Vậy `x in { -4 ; 3 }`