\(a)x(x+2)=3x+6\\<=>x(x+2)-(3x+6)=0\\<=>x(x+2)-3(x+2)=0\\<=> (x+2)(x-3)=0\\<=>\left[\begin{matrix} x+2=0\\ x-3=0\end{matrix}\right.\\<=> \left[\begin{matrix} x=-2\\ x=3\end{matrix}\right.\\b)4x^2-9+(2x-3)^2=0\\<=>(2x-3)(2x+3)+(2x-3)^2=0\\<=>(2x-3)(2x+3+2x+3)=0\\<=> (2x-3)(4x+6)=0\\<=>\left[\begin{matrix} 2x-3=0\\ 4x+6=0\end{matrix}\right.\\<=>x=3/2 hoặc -3/2\)