\(\Leftrightarrow2\left(x^2-2x-3\right)=2x^2+7x+3-12\)
\(\Leftrightarrow2x^2-4x-6-2x^2-7x+9=0\)=
=>3-11x=0
hay x=3/11
(2x2 - 6)(x - 1) = (2x + 1)(x + 3) - 12
2x2- x - 6x + 6 = 2x2+ 6x + x + 3 - 12
2x2 - 2x -6x + 6 - 2x2 - 6x - x - 3 + 12 = 0
-15x -15 =0
-15x = 15
x= -1