`#Sad`
`7)`
`4(2x+1) = 3x(-2x-1)`
`⇔ 8x+4 = -6x^2-3x`
`⇔ 6x^2+8x+3x+4 = 0`
`⇔ 6x^2+11x+4 = 0`
`⇔ 6x^2+8x+3x+4 = 0`
`⇔ (6x^2+3x)+(8x+4) = 0`
`⇔ 3x(2x+1)+4(2x+1) = 0`
`⇔ (3x+4)(2x+1) = 0`
`⇔` \(\left[ \begin{array}{l}3x+4=0\\2x+1=0\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}3x=-4\\2x=-1\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x=-\dfrac{4}{3}\\x=-\dfrac{1}{2}\end{array} \right.\)
`\text{Vậy S=}` `{-4/3; -1/2}`
