`2x(3x+6)=0`
`⇔x(x+2)3=0`
`⇔x(x+2)=0`
`⇔`\(\left[ \begin{array}{l}x=0\\x+2=0\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=0\\x=-2\end{array} \right.\)
`3+2x=0`
`⇔2x=-3`
`⇔x=-3/2`
`6x-(3x+2).(3x+2)=0`
`⇔6x-9x^2-6x-6x-4=0`
`⇔-9x^2-6x-4=0`
`⇔9x^2+6x+4=0`
`⇔(3x+1)^2+3=0`
`⇒`vô nghiệm